Ever since I switched, I see "Connected" in the RCS status but I don't actually have RCS chats.
Apparently this is because Google is silently blocking RCS on phones running custom ROMs. Yet another example of adding insult to the injury of refusing to release updates for my phone model from them!
I could root my phone to fix this, an annoying process I didn't really want to do, and it would ironically make it a bit less secure though then be able to fool Google into actually treating it as secure. Or, I could find some other messaging app for this, though I'd ideally want one that was self-hostable for a sync to a desktop client somehow. I'd lazily been just using Google Messages for that, but Google is doing their best to dissuade me from using their products . . .