In the end you could use any distro which desktop you like (which could be Debian stable, or something immutable) and then get your applications from the latest and greatest with Distrobox

If you like web tools maybe https://github.com/Frooodle/Stirling-PDF could be something for you.

I do remember my joy, when finding out that instead of feeding it with batteries, I could even use the power adapter of the master system to play with the Gamegear. 😄

Another +1 for restic. To simplify the backup I am however using https://autorestic.vercel.app/, which is triggered from systemd timers for automated backups.