I don't believe it is a different in OMV 6 and 7. I think the difference is between the docker-ce package for Debian 11 and 12.
I just copied your airsonic and navidrome yml to my omv7 dev system (amd64( and the web interface works fine on both. I'm not sure why armhf has an issue. The plugin is installing docker the same way.
Thanks for giving it a try. Then it might be really an issue with Debian 12 and the armhf environment.
Meanwhile I rolled back to OMV6 on Debian 11 and everything works as expected. I will probably just leave it as it is for now. The HC1 is just perfect as a little media server and even my wife does not complain because it's tiny and noiseless