HI Doug
I'm running into the same problem here using beagleboard black running ubuntu-dsktop on a sd card the /sys/class/drm/card0-HDMI-A-1/enabled shows disabled
cat /proc/cmdline shows this
console=ttyO0,115200n8 video capemgr=capemgr.enable_partno=BB-BONELT-HDMI root=/dev/mmcblk0p2 ro rootfstype=ext4 rootwait
ubuntu@ubuntu-armhf:~$ cat /sys/devices/bone_capemgr.9/slots
0: 54:PF---
1: 55:PF---
2: 56:PF---
3: 57:PF---
4: ff:P-O-L Bone-LT-eMMC-2G,00A0,Texas Instrument,BB-BONE-EMMC-2G
5: ff:P-O-L Bone-Black-HDMI,00A0,Texas Instrument,BB-BONELT-HDMI
can u show me your uenv file? thx i try to edit my uenv doesn't work
best
jason