I use Resilio Sync, and have tried SyncThing. Both work. They both have an app you run in your phone, and a companion app you run on macOS, Windows, Linux, or

I use Resilio Sync, and have tried SyncThing. Both work. They both have an app you run in your phone, and a companion app you run on macOS, Windows, Linux, or your NAS, and it syncs (even through a NAT) whatever you've configured to backup on your phone to N servers. If you're away from home, you can run it on your laptop next to you, so your phone is backed up quickly, and then throughout the day you laptop can sync with your home server while you're out exploring. It's nice. I have two backups online, and an external drive I rsync to monthly then turn off. Before you delete your originals in Google Photo, use Takeout to validate the files. Mine (at "original quality") were mangled.