Comment by grapheneos

RCS is fully functional on GrapheneOS. Google Messages is the only implementation of RCS available for Android in practice. RCS is a proprietary Google messaging system in practice. Google hosts a huge portion of the infrastructure and gatekeeps access to it. It would be possible to make an alternative RCS client for Android but it would still using Google infrastructure since carriers are using it.

> 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.

GrapheneOS is not about specifically avoiding Google apps and services. You've said you want to use Google's RCS messaging system, which would not take away from the benefits of using GrapheneOS.

> a weird privacy focused OS

GrapheneOS is a widely used open source project. It's well known and there's nothing unusual about using it. The hypothetical situation you're describing is not something which has ever been known to happen.

> Also the backup restoration is a bit more of a mess for me right now

GrapheneOS has better backup/restore support than the stock OS. It doesn't have privileged Google Play integration for using Google's very limited app backup/restore or their more capable device transfer feature. GrapheneOS has an equivalent to the device transfer feature which can be used for both encrypted local and cloud backups.

> dual sim feature

GrapheneOS fully supports cross-SIM calling and it's one of the features it adds the option to force enable for carriers not otherwise supporting it alongside 5G, VoLTE, Vo5G and VoWiFi