Tom - look at the recent GW1000 thread in the -user group please.
If you install Gary's GW1000 driver with a .deb weewx of 5.0b10 there seems to be some mismatch of where extensions are installed.
Installing his driver in a .deb puts it into /etc/weewx/user but then weectl extension list cannot find it. It was necessary to cp -a /etc/weewx/user/* to /usr/share/weewx/user to get the extension to become visible and work ok after a station reconfigure.
(I recreated his issue and tested both a .deb (broken) and pip (ok) installation)
Details over in that thread.....