Beagleboard:BeagleBone Debian Image Migration

cape-universal
''Help! My overlay won't load! There's just this weird cape in slot 4.''

You've met "cape-universal". It is meant to often make overlays unnecessary, but you can also just disable it by changing the following line in /boot/uEnv.txt: cmdline=coherent_pool=1M quiet cape_universal=enable to cmdline=coherent_pool=1M quiet

Disabling eMMC or HDMI
HDMI and eMMC are now part of the main dtb instead of being virtual CAPEs, which means that to disable these you change the 'dtb' variable in /boot/uEnv.txt instead of using capemgr.disable_partno:

See also this survey of BeagleBone DTBs.