Ok, thank you for you patience. Even tho the idea with the Bookworm is interesting I probably won't try it, sorry.

@wolfyn-claw I have had similar problems experimenting with Ubuntu 64bit. I don’t believe your going to get much help with that. However you could try installing retropie on raspberry pi is beta 64 version. It worked for me.

Support for ARM64 is just preliminary in RetroPie (not only for Amiberry). If an emulator is not enabled, it means it hasn't been tested and the installation script hasn't been updated for that platform. There's no need for a request, support for Amiberry will probably be added at some point.