Various HDD full data backups maintained with FreeFileSync, important files backup on ProtonDrive. Multi-device autosync with Syncthing (phones, tablet, pcs)

Termux gang

I’m also interested in this, I use Syncthing for multi-device sync, but it’s not aimed for multi-directoy in a single device backup

But, syncthing does not allow single-device synchronization, is a multi-device sync app