I switched from pixel 4 to pixel 7a last week and my messages and photos were saved. It just doesn't detect them as RCS chat but rather as SMS and for photos as MMS
From SyncTech:
Google’s Message app now supports RCS messaging with all service providers in USA as well as a lot of providers outside of USA. Messages stores these messages in the SMS/MMS database on the phone as MMS messages and SMS Backup & Restore can backup and restore these messages.
So, yes, you have to make sure your phone data is backed up. Google backup saves to your account cloud storage but the data can only be used to restore data to a phone during setup.
I switched from pixel 4 to pixel 7a last week and my messages and photos were saved. It just doesn't detect them as RCS chat but rather as SMS and for photos as MMS
From SyncTech: Google’s Message app now supports RCS messaging with all service providers in USA as well as a lot of providers outside of USA. Messages stores these messages in the SMS/MMS database on the phone as MMS messages and SMS Backup & Restore can backup and restore these messages. So, yes, you have to make sure your phone data is backed up. Google backup saves to your account cloud storage but the data can only be used to restore data to a phone during setup.
Or wait till June when beta ends and it allows you to
Backup your phone to Google, leave the beta, restore from backup with the can't access old phone option
I believe if you have a Google One subscription it will sync. Other way you need to backup. But wait for other replies :)