Robduarte
Having read the forums on RCS, why do you think its going to work reliably or will it be easy to set up. Some apps work like clockwork and prove no bother at all, yet some are reliably unreliable, you have chosen one of them. Just look at the post below, over a thousand posts and still RCS works when it wants.
https://discuss.grapheneos.org/d/1353-using-rcs-with-google-messages-on-grapheneos/1124
I would learn from the past mistakes of others and leave RCS alone.
Problem being that the cohort of people you want to comunicate with use RCS and are quite happy to carry on using RCS, leaving you as the outlier on GrapheneOS.
GrapheneOS is not for everyone and maybe it does not fit with what you need, it maybe what you want but not quite what you need.