I ended up using a combination of Obsidian sync and Google drive to do what I wanted, and it was much easier.

I'm all for people using Syncthing in cases where it meets their needs, but when you're mainly syncing notes, I think it's overkill and doesn't pull its weight in terms of its learning curve and the potential to screw things up with an incorrect configuration.

Another issue I ran into was that the devices have to be awake at the same time to sync between them. Using a cloud based solution makes that problem go away. Syncthing might be worth it for me if I ever get around to setting up a Linux media server, but I've been resisting it because I don't want another machine to maintain. I still can't help but think of an old job I had where we were almost unable to do a big demo because it relied on a server at a coworker's house that was accidentally unplugged.