According to the release notes for GOS v20250927:
This release adds official support for using RCS in Google Messages. Using this requires granting the Phone permission to Play services to provide carrier information to it, granting the required permissions to Google Messages and then setting Google Messages as the current carrier messaging app.
How, specifically, do we do that? I'm stuck at the first step. Under Settings > Apps > Phone > Permissions, Play services is nowhere to be found. Perhaps I'm going about it backwards? But, under Settings > Apps > Google Play Services > Permissions, it already has Phone permission.
Then, what does it mean by "granting the required permissions to Google Messages?" Nothing leaps out at me under Settings > Apps > Messages > Permissions about RCS. Within Messages, itself, under its Settings, I've already got RCS turned on and it claims it's connected to my T-Mobile phone number. But, RCS doesn't appear to be active in the Contacts where it should be (it used to be, but it seems to have disappeared fairly recently). For instance, my spousal unit's Google Messages shows RCS for me. But, I still show text message for her.
Google Messages is installed from the Play Store (along with Carrier Services). I assume it's the current carrier messaging app since it's where SMS messages go when I get one. But, where do I actually confirm that?