Android - Does Titanium Backup backup the Signal private Key?
Signal 4.17.0 introduced encrypted backups. This is the preferred migration path. Also the Titanium Backup route does not work in current releases.
I just tried this and it worked flawlessly.
After restoring Signal on your new Phone you should re-activated your connection by unregistering and re-registering to the Signal servers. As of now you can do this in the Signal Settings > Advanced tab by toggleing Signal messages to de-activate then re-activate . In this Process you will have to re-verify your phone number and you'll have to reconnect your Signal-Desktop clients afterwards.
You won't loose your Private key or your Signal-Desktop messages though.
Titanium Backup does backup the key, but there's something internal to Signal that realises that it's installed on a new phone and refuses to use the old key.
Set recurring backups inside Signal instead.
Be aware that when restoring:
.backup file in the sdcard root directory. Putting it under
sdcard/Signal/backups will have the file NOT be read, but no error message given, either.
The backup is only read correctly if the metadata is displayed in a confirmation step. This took me hours to work out. >:|