Today I had an unexpected reboot and was shocked (but pleased) to see the current stable (bullseye) named started without problems!
I checked "aa-remove-unknown -n" output (as in my previous update) but this time there was no mysterious "/usr/sbin/named" profile to be removed, and with it not in the picture the expected profile was in place and everything is great. I still have no idea where that weird profile came from or why it disappeared. I was under the impression that "aa-remove-unknown" is only unloading profiles from memory, and not making persistent changes, but I can't think of anything else that's happened recently. In any case, I no longer observe this problem and I would be happy to see this bug report closed. Thanks for putting up with me for 16 months, Scott