There have been consistent problems with activating RCS, for many years. But it does work for some/many, yes.

And AFAIK they have only been desiring to build their own RCS app, and researching it, but have no concrete plans. It'll probably be extremely hard to do, given how much interaction it requires with individual telecoms, and how large the specs are and how much they change - it'll be signing up for significant dedicated eng/business/etc effort that will never decrease. Though I would very much like it if it does happen.

Personally: it worked for about a year for me, then stopped for several months, then worked for two, then I disabled it. All on the same phone, same OS install, same carrier and phone plan, and same location. No issues at all on stock Android with everything else identical which my wife uses. You can find tons of cases like this with Graphene users, RCS just doesn't work/activate/??? as well for some reason.