One of the best pieces of open source software that I use all the time is Syncthing.
It just works. It is so good.
My main use case is that I have an old PC that I use to connect to a 1990s film scanner. I got tired of using all kinds of portable hard drives to move stuff from one computer to another.
I have a NAS set up at home and I just do Syncthing on the NAS and the PC so it's always uploaded with the latest scans.
Later I pull the files I want into my Mac to do more work on the digital negatives.
@skinnylatte Just curious—what scanner? I still have an Epson V300 I haven’t used since my early film photography days scanning negatives and slides.
@genxjamerican I have a Plustek 8200i and a Nikon CoolScan 8000ED