Signal now uses the Android hardware keystore such that you cannot use a root app like TiBackup to move the Signal data around anymore. Instead you have to use Signal's built-in backup and then place the backup on the new phone and setup Signal again (generating a new ID key).
I've used both. You can use ti to move the signal specific backup over. Did this just a few days ago.
That seems nicer than the method without Ti requiring you to find the backup and move it 'by hand' to the right place on the new phone.