Thanks Dirk!
Logs attached.
I tried plugging in the DiveMate without having Subsurface open, and it opened automatically, so it seems that's set up to handle DiveMate.
The rescan button is greyed out until I turn on Bluetooth, as you can see it sees Bluetooth speakers I've previously connected, but not DiveMate.
---------- subsurface.log ----------
"0.002: Successfully opened logfile /storage/emulated/0/subsurface.log at Sat Sep 5 20:47:11 2020"
"0.002: Starting Subsurface-mobile:3.0.13(4.9.6.28):Android (10.0):arm64:en-GB"
"0.002: built with libdivecomputer v0.7.0-devel-Subsurface-NG (6935fe717ac73402c589c2ccc435ad8efd60cd50)"
"0.002: built with Qt Version 5.13.2, runtime from Qt Version 5.13.2"
"0.002: built with libgit2 0.26.0"
"0.002: Running on Android (10.0)"
"0.002: ONEPLUS A6013/OnePlus/OnePlus6TSingle"
BTDiscoveryReDiscover: localBtDevice.isValid() true
localBtDevice isn't valid or not connectable
"0.007: Created position source android"
"0.008: Set GPS service update interval to 300 s"
"0.008: location service is available"
qrc:/qml/TripDetails.qml:30: TypeError: Cannot read property 'width' of null
"0.047: download page -- looking for known BT/BLE device"
qrc:/org/kde/kirigami/ScrollablePage.qml:187: TypeError: Cannot assign to read-only property "parent"
"0.053: Window width changed to 660 orientation 1"
"0.053: Screen rotated, no action necessary"
"0.054: 1 columns with column width of 660"
"0.054: width in Grid Units 30 original gridUnit 22 now 22"
"0.054: Done setting up sizes"
"0.114: StartPage visibility changed to false"
"0.115: not yet initialized, show busy spinner"
content height changed
"0.530: finished setting up the diveListView"
"0.531: StartPage completed -- initialized is false"
"0.531: screenSizeObject constructor completed, initial width 660"
"0.531: 1 columns with column width of 660"
"0.531: width in Grid Units 30 original gridUnit 22 now 22"
"0.531: Done setting up sizes"
qrc:/org/kde/kirigami/AbstractApplicationHeader.qml:57: TypeError: Cannot read property 'header' of null
qrc:/org/kde/kirigami/ContextDrawer.qml:92: TypeError: Cannot call method 'hasOwnProperty' of null
loaded main.qml
qqwindow devicePixelRatio 3.00071 3.00071
qml_window reports width as 660 associated screen width 360 Qt screen reports width as 360
QMLManager received screen changed notification (360,705)
qqwindow screen has ldpi/pdpi 71.983 135.583
"0.657: Window width changed to 360 orientation 1"
"0.657: first real change, so recalculating units and recording size as 360 x 705"
"0.660: 1 columns with column width of 360"
"0.660: width in Grid Units 21 original gridUnit 22 now 17"
"0.680: Done setting up sizes"
"0.766: Window width changed to 510 orientation 1"
"0.767: size change without rotation to 510 x 765"
"0.767: resetting to initial width 360 and height 705"
"0.817: Window width changed to 360 orientation 1"
"0.818: size change without rotation to 360 x 705"
"0.945: AppState changed to active with no unsaved changes"
"0.945: finishSetup called"
qrc:/org/kde/kirigami/templates/private/ScrollView.qml:95:5: QML QQuickItem: ScrollBar must be attached to a Flickable or ScrollView
"0.973: showProgress: populate data model"
"0.981: showProgress: start processing"
"0.996: showProgress: 0 dives processed"
"1.013: showProgress: finish populating data store"
"1.029: showProgress: setting up internal data structures"
"1.061: showProgress: done setting up internal data structures"
"1.064: ============diveListProcessing is true"
"1.064: showProgress: Open local dive data file"
"1.064: showProgress: Synchronising data file"
"1.066: showProgress: Load dives from local cache"
"1.179: showProgress: Successfully opened dive data"
"1.206: showProgress: Processing 832 dives"
"1.214: showProgress: Create full text index"
"1.230: showProgress: start processing"
"1.256: showProgress: 832 dives processed"
"1.288: showProgress: populate data model"
"1.300: showProgress: start processing"
"1.323: showProgress: 832 dives processed"
"1.331: showProgress: finish populating data store"
"1.507: showProgress: setting up internal data structures"
"1.598: showProgress: done setting up internal data structures"
"1.604: showProgress: 832 dives loaded from local dive data file"
"1.619: have cloud credentials, but user asked not to connect to network"
"1.630: ============diveListProcessing is false"
"1.631: initialization completed - showing the dive list"
"1.649: pageStack switched to DiveList"
"1.678: switched to page Dive list"
index 1 select changed to true
updated view.currentIndex
"1.750: if we got started by a plugged in device, switch to download page -- pluggedInDeviceName = "
"1.751: called by connect intent for device Cressi [1:3]"
"1.752: rescanning USB: 5 devices reported"
"1.753: found USB device with ui string Cressi [1:3] (CdcAcmSerialDriver)"
"1.754: found USB device with ui string Cressi [1:3] (Ch34xSerialDriver)"
"1.755: found USB device with ui string Cressi [1:3] (Cp21xxSerialDriver)"
"1.756: found USB device with ui string Cressi [1:3] (FtdiSerialDriver)"
"1.757: found USB device with ui string Cressi [1:3] (ProlificSerialDriver)"
BTDiscoveryReDiscover: localBtDevice.isValid() true
localBtDevice isn't valid or not connectable
"1.759: plugged in device name changed to 6;-1;0"
"1.759: show download page for 6 / -1 / 0"
"1.767: pageStack switched to "
"1.768: switched to page Dive Computer"
checkPendingIntents
"LocalDeviceBroadcastReceiver::onReceive() - event: android.bluetooth.adapter.action.SCAN_MODE_CHANGED"
btHostModeChange to QBluetoothLocalDevice::HostConnectable
BTDiscoveryReDiscover: localBtDevice.isValid() true
"BTDiscoveryReDiscover: localDevice OnePlus 6T is powered on, starting discovery"
paired BT classic device type 1 with address "70:26:05:DD:4C:F6"
paired BT classic device type 1 with address "E8:07:BF:33:DB:7C"
Found new device: "WH-H900N (h.ear)" "70:26:05:DD:4C:F6"
Not recognized as dive computer
Found new device: "Mi Bluetooth Speaker" "E8:07:BF:33:DB:7C"
Not recognized as dive computer
Paired = "WH-H900N (h.ear)" "70:26:05:DD:4C:F6"
Paired = "Mi Bluetooth Speaker" "E8:07:BF:33:DB:7C"
"55.572: rescanning USB: 5 devices reported"
"55.572: found USB device with ui string Cressi [1:3] (CdcAcmSerialDriver)"
"55.578: found USB device with ui string Cressi [1:3] (Ch34xSerialDriver)"
"55.579: found USB device with ui string Cressi [1:3] (Cp21xxSerialDriver)"
"55.580: found USB device with ui string Cressi [1:3] (FtdiSerialDriver)"
"55.581: found USB device with ui string Cressi [1:3] (ProlificSerialDriver)"
BTDiscoveryReDiscover: localBtDevice.isValid() true
"BTDiscoveryReDiscover: localDevice OnePlus 6T is powered on, starting discovery"
paired BT classic device type 1 with address "70:26:05:DD:4C:F6"
paired BT classic device type 1 with address "E8:07:BF:33:DB:7C"
Found new device: "WH-H900N (h.ear)" "70:26:05:DD:4C:F6"
Not recognized as dive computer
Found new device: "Mi Bluetooth Speaker" "E8:07:BF:33:DB:7C"
Not recognized as dive computer
Paired = "WH-H900N (h.ear)" "70:26:05:DD:4C:F6"
Paired = "Mi Bluetooth Speaker" "E8:07:BF:33:DB:7C"
qrc:/qml/DownloadFromDiveComputer.qml:208: ReferenceError: disableDC is not defined
"63.669: rescanning USB: 5 devices reported"
"63.669: found USB device with ui string Cressi [1:3] (CdcAcmSerialDriver)"
"63.676: found USB device with ui string Cressi [1:3] (Ch34xSerialDriver)"
"63.677: found USB device with ui string Cressi [1:3] (Cp21xxSerialDriver)"
"63.678: found USB device with ui string Cressi [1:3] (FtdiSerialDriver)"
"63.679: found USB device with ui string Cressi [1:3] (ProlificSerialDriver)"
BTDiscoveryReDiscover: localBtDevice.isValid() true
"BTDiscoveryReDiscover: localDevice OnePlus 6T is powered on, starting discovery"
paired BT classic device type 1 with address "70:26:05:DD:4C:F6"
paired BT classic device type 1 with address "E8:07:BF:33:DB:7C"
Found new device: "WH-H900N (h.ear)" "70:26:05:DD:4C:F6"
Not recognized as dive computer
Found new device: "Mi Bluetooth Speaker" "E8:07:BF:33:DB:7C"
Not recognized as dive computer
Paired = "WH-H900N (h.ear)" "70:26:05:DD:4C:F6"
Paired = "Mi Bluetooth Speaker" "E8:07:BF:33:DB:7C"
qrc:/qml/DownloadFromDiveComputer.qml:208: ReferenceError: disableDC is not defined
"81.277: rescanning USB: 5 devices reported"
"81.278: found USB device with ui string Cressi [1:3] (CdcAcmSerialDriver)"
"81.284: found USB device with ui string Cressi [1:3] (Ch34xSerialDriver)"
"81.285: found USB device with ui string Cressi [1:3] (Cp21xxSerialDriver)"
"81.287: found USB device with ui string Cressi [1:3] (FtdiSerialDriver)"
"81.287: found USB device with ui string Cressi [1:3] (ProlificSerialDriver)"
BTDiscoveryReDiscover: localBtDevice.isValid() true
"BTDiscoveryReDiscover: localDevice OnePlus 6T is powered on, starting discovery"
paired BT classic device type 1 with address "70:26:05:DD:4C:F6"
paired BT classic device type 1 with address "E8:07:BF:33:DB:7C"
Found new device: "WH-H900N (h.ear)" "70:26:05:DD:4C:F6"
Not recognized as dive computer
Found new device: "Mi Bluetooth Speaker" "E8:07:BF:33:DB:7C"
Not recognized as dive computer
Paired = "WH-H900N (h.ear)" "70:26:05:DD:4C:F6"
Paired = "Mi Bluetooth Speaker" "E8:07:BF:33:DB:7C"
"82.575: rescanning USB: 5 devices reported"
"82.576: found USB device with ui string Cressi [1:3] (CdcAcmSerialDriver)"
"82.581: found USB device with ui string Cressi [1:3] (Ch34xSerialDriver)"
"82.582: found USB device with ui string Cressi [1:3] (Cp21xxSerialDriver)"
"82.583: found USB device with ui string Cressi [1:3] (FtdiSerialDriver)"
"82.585: found USB device with ui string Cressi [1:3] (ProlificSerialDriver)"
BTDiscoveryReDiscover: localBtDevice.isValid() true
"BTDiscoveryReDiscover: localDevice OnePlus 6T is powered on, starting discovery"
paired BT classic device type 1 with address "70:26:05:DD:4C:F6"
paired BT classic device type 1 with address "E8:07:BF:33:DB:7C"
Found new device: "WH-H900N (h.ear)" "70:26:05:DD:4C:F6"
Not recognized as dive computer
Found new device: "Mi Bluetooth Speaker" "E8:07:BF:33:DB:7C"
Not recognized as dive computer
Paired = "WH-H900N (h.ear)" "70:26:05:DD:4C:F6"
Paired = "Mi Bluetooth Speaker" "E8:07:BF:33:DB:7C"
"96.299: setDevName matches USB device 0"
"96.301: DCDownloadThread started for Cressi Leonardo on Cressi [1:3] (CdcAcmSerialDriver) downloading only new dives"
Starting download from Cressi [1:3] (CdcAcmSerialDriver)
downloading only new dives
"96.308: Opening serial device Cressi [1:3] (CdcAcmSerialDriver)"
Finishing download thread: "Unable to open Cressi [1:3] (CdcAcmSerialDriver) Cressi (Leonardo)"
"96.327: Input/output error"
"96.380: no new dives downloaded"
"96.381: DCDownloadThread finished"
"99.581: setDevName matches USB device 0"
"99.581: DCDownloadThread started for Cressi Leonardo on Cressi [1:3] (CdcAcmSerialDriver) downloading only new dives"
Starting download from Cressi [1:3] (CdcAcmSerialDriver)
downloading only new dives
"99.585: Opening serial device Cressi [1:3] (CdcAcmSerialDriver)"
Finishing download thread: "Unable to open Cressi [1:3] (CdcAcmSerialDriver) Cressi (Leonardo)"
"99.595: Input/output error"
"99.596: no new dives downloaded"
"99.596: DCDownloadThread finished"
"112.046: setDevName matches USB device 1"
"112.047: DCDownloadThread started for Cressi Leonardo on Cressi [1:3] (Ch34xSerialDriver) downloading only new dives"
Starting download from Cressi [1:3] (Ch34xSerialDriver)
downloading only new dives
"112.050: Opening serial device Cressi [1:3] (Ch34xSerialDriver)"
Finishing download thread: "Unable to open Cressi [1:3] (Ch34xSerialDriver) Cressi (Leonardo)"
"112.069: Input/output error"
"112.143: no new dives downloaded"
"112.144: DCDownloadThread finished"
"119.904: setDevName matches USB device 2"
"119.906: DCDownloadThread started for Cressi Leonardo on Cressi [1:3] (Cp21xxSerialDriver) downloading only new dives"
Starting download from Cressi [1:3] (Cp21xxSerialDriver)
downloading only new dives
"119.909: Opening serial device Cressi [1:3] (Cp21xxSerialDriver)"
"119.921: Connecting ..."
"120.229: Starting import ..."
"120.278: No new dives downloaded from dive computer"
Finishing download thread: "Dive data import error"
"120.361: no new dives downloaded"
"120.362: DCDownloadThread finished"
"128.798: setDevName matches USB device 3"
"128.799: DCDownloadThread started for Cressi Leonardo on Cressi [1:3] (FtdiSerialDriver) downloading only new dives"
Starting download from Cressi [1:3] (FtdiSerialDriver)
downloading only new dives
"128.802: Opening serial device Cressi [1:3] (FtdiSerialDriver)"
"128.812: Connecting ..."
"129.117: Starting import ..."
"130.134: No new dives downloaded from dive computer"
Finishing download thread: "Dive data import error"
"130.220: no new dives downloaded"
"130.221: DCDownloadThread finished"
"136.409: setDevName matches USB device 4"
"136.410: DCDownloadThread started for Cressi Leonardo on Cressi [1:3] (ProlificSerialDriver) downloading only new dives"
Starting download from Cressi [1:3] (ProlificSerialDriver)
downloading only new dives
"136.413: Opening serial device Cressi [1:3] (ProlificSerialDriver)"
Finishing download thread: "Unable to open Cressi [1:3] (ProlificSerialDriver) Cressi (Leonardo)"
"136.433: Input/output error"
"136.514: no new dives downloaded"
"136.515: DCDownloadThread finished"
"146.573: setDevName matches USB device 4"
"146.574: DCDownloadThread started for Cressi Leonardo on Cressi [1:3] (ProlificSerialDriver) downloading only new dives"
Starting download from Cressi [1:3] (ProlificSerialDriver)
downloading only new dives
"146.578: Opening serial device Cressi [1:3] (ProlificSerialDriver)"
"146.596: Input/output error"
Finishing download thread: "Unable to open Cressi [1:3] (ProlificSerialDriver) Cressi (Leonardo)"
"146.599: no new dives downloaded"
"146.599: DCDownloadThread finished"
QMetaObject::invokeMethod: No such method QQuickButton::inputMethodQuery(Qt::InputMethodQuery,QVariant)
"165.622: setDevName matches USB device 4"
"165.623: DCDownloadThread started for Cressi Leonardo on Cressi [1:3] (ProlificSerialDriver) downloading only new dives"
Starting download from Cressi [1:3] (ProlificSerialDriver)
downloading only new dives
"165.627: Opening serial device Cressi [1:3] (ProlificSerialDriver)"
"165.643: Input/output error"
Finishing download thread: "Unable to open Cressi [1:3] (ProlificSerialDriver) Cressi (Leonardo)"
"165.645: no new dives downloaded"
"165.646: DCDownloadThread finished"
"169.440: setDevName matches USB device 4"
"169.441: DCDownloadThread started for Cressi Leonardo on Cressi [1:3] (ProlificSerialDriver) downloading all dives"
Starting download from Cressi [1:3] (ProlificSerialDriver)
downloading all dives
"169.447: Opening serial device Cressi [1:3] (ProlificSerialDriver)"
Finishing download thread: "Unable to open Cressi [1:3] (ProlificSerialDriver) Cressi (Leonardo)"
"169.474: Input/output error"
"169.475: no new dives downloaded"
"169.475: DCDownloadThread finished"
qrc:/org/kde/kirigami/templates/private/ScrollView.qml:113:9: QML ScrollBar: Binding loop detected for property "visible"
"187.409: pageStack switched to "
"187.411: switched to page About Subsurface-mobile"
"187.411: endEditMode called with state view"
---------- libdivecomputer.log ----------
Subsurface: v4.9.6-28-g2c878ea6b634, built with libdivecomputer v0.7.0-devel-Subsurface-NG (6935fe717ac73402c589c2ccc435ad8efd60cd50)
---------- finish ----------