Regarding backing up without reboot, I have written about my backup process here
Note that this doesn’t back up applications themselves, because they can be reinstalled from App Lounge or F-Droid.
Another manual approach (vs sync to murena.io) is to connect your phone to a PC in file transfer mode, and copy all your documents, photos, app settings etc to the PC.
Perhaps not perfect, but it will preserve personal files, which I assume will be the most valuable to you.