RCS successfully works, verified on 4 phones (two p7p, p8, p9p) all run GOS two separate carriers. This is all you need, fairly basic permissions: #13531187 If you haven't fiddled with anything since before it stopped working then all you need to do is apply the GOS update.
mousetrapreplica however only SMS was sending
As for people installing old versions of google messages. DO NOT DO THIS all you will do is rate limit yourself and then it won't work at all. A version of Google Messages from 2024 certainly will not work correctly.
If you are rate limited, i suggest turning off RCS and disabling RCS https://messages.google.com/disable-chat for good measure. Come back in 3 days and try again.
For one of my devices that was rate limited, I turned RCS off on the 8th and tried again today and it worked instantly.