SyncThing is probably my most used bit of software after LibreWolf. I have it installed on all of the computers I use so I have damn near instant, magical access to a bunch of files. It's how I sync my photos from my Pixel.

It's funny, because SyncThing is basically the reason I barely use my iPad these days. While there is a way to make it work with iOS, it's irritating enough that I just don't bother, and I don't use iCloud storage anymore, so it's a pain in the arse getting documents to it compared to just dropping them in a ST folder that my phone can access.