If you are on an Android device you can export an encrypted backup and scan a QR code / type in the password to the encrypted archive to transfer messages / group memberships with only a safety number change in most cases.
I think that's the opposite of what I want? I want to inform people of the new safety number using the old channel and purge all data like a good user.
In this respect a keybase like model makes more sense to me.
Two small corrections: Signal-Android's backup works with a passphrase only (no QR codes involved) and does not cause safety number changes on restore.
In this respect a keybase like model makes more sense to me.