My understanding was that you have to install google messages to get RCS to work and on google's end it gets finicky about device ids. I read a couple blogs where people found RCS to be really unstable on GrapheneOS even with a couple workarounds.

If I'm going to have to install a bunch of google products onto my phone anyways, I don't buy the benefits as much.

I also had a recent experience being shaken down by a border guard entering Australia, and if he'd asked to go through my phone, explaining that I'm running a weird privacy focused OS he's never seen before seems like it would be a great way to increase my chances of spending a night in airport jail and being put on the next flight to North America. I don't really have anything to hide and appearing like I have things to hide could seriously inconvenience my life. Barring a tourist from entering a country has a very low bar of evidence.

Edit: Also the backup restoration is a bit more of a mess for me right now for the same reason I need the dual sim feature. I've got an American esim that's difficult to reactivate without being in America.

RCS is unstable on iOS, too,

for the same reasons SMS has always been unstable.

It’s the nature of the protocol, unfortunately.