ErnestThornhill
Same here with my Pixel 7 Pro with sandboxed Google Play Services and my Pixel 8 Pro w/o Google.
Default Android App for SMS/MMS isn't sending anymore (haven't tested other apps)!
Receiving is possible, have that tested with my old iPhone Xs.
Three Test SMS from iPhone to my Pixel 8 Pro, all successful received.
I guess, the reason for that is Googles new RCS app, maybe Google forces RCS with Android 15 more then before and force the user to select their newest RCS app.
But GOS hasn't this app and so it must fail…
The SMS app menus don't look complete either, plus the buttons are greyed out and most of them are non-functional. Strangely, not all of them are dead either, so something is wrong...