Success
Had already running Catalina on OpenCore 0.6.1, updated the kexts and rebooted.
Then I updated to OpenCore 0.6.3 and still no problems.
Finally updated to Big Sur with no problems.
Did not have iMessage running on Catalina, so still doesn't work.
I can't find my Denon receiver as normal sound output, but don't know if it is a setting or a bug (was working in Catalina).
It is visible when I open Apple Music.