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

cape-universal is also automatically disabled if  occurs in the kernel cmdline (even if its argument is blank) or any overlay is already applied via capemgr before cape-universal can be loaded.

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.