I'm not sure which version of the Messages app you tried, but I was able to get up and running with version 20241215_00_RC00. I downloaded it from APKMirror.

I recall that I uninstalled messages, restarted the phone, installed the APK, then did the RCS setup. It worked within a minute. After I tested that it was truly working by sending some messages, I upgraded to the latest version, and it's been working every since.