I'll add to the pile of people suggesting syncthing. Works great across several PCs and phones for me. Mostly GNU/Linux and Android, a Windows machine or two, a

I'll add to the pile of people suggesting syncthing. Works great across several PCs and phones for me. Mostly GNU/Linux and Android, a Windows machine or two, and I think I put it on one Mac that I don't use often. I also have it on my Steam Deck. As some others also mentioned, syncing is not a true backup and you'll still want to make periodic copies to another drive/machine, probably at least one copy off-site. I just use rsync to a physical server at another location I have access to, but seems like many are recommending rclone for use with cloud storage.