If this works, I will eat my hat and maybe six other hats. Not only does the open-source Syncthing allow you to sync files between any number of computers running any number of operating systems (including Windows, Mac, Linux and ALL of the BSDs), it does this WITHOUT NEEDING A SERVER. The client software appears to handle the whole thing.

If I understand it correctly, the clients "talk" to each other, and there is no server or cloud service to maintain or pay for.

If this works, it looks like you can replace Dropbox, Google Drive, Microsoft OneDrive, Box, and any number of cloud-based services that cost money and very likely don't work on your non-Windows/Mac hardware.

I give Dropbox extreme credit for always having a Linux client and not being a total and complete hypocrite like Google, who build their entire infrastructure off of Linux, give their developers Linux computers, base Chrome OS on Linux yet can't be bothered to release a Linux client for their consumer/business storage service. I'm not expecting Microsoft to release a Linux client for OneDrive, but Google? Come on!

Right now I use Dropbox, but I wish I had many alternatives. I like SpiderOak, and they do offer a Linux client, so that's a service to consider.

NextCloud and the project that spawned it, OwnCloud, offer a store-your-own file setup, and they do offer Linux clients.

But since I've been playing around with OpenBSD again, it would be nice to be able to sync to that OS, and the lack of Dropbox compatibility has kept me from fully using OpenBSD. Syncthing does offer OpenBSD software, and it would be great to have that capability.

If Syncthing lives up to the hype, it'll be the world's biggest game-changer for me. But how CAN it work if all of the client computers aren't turned on simultaneously? That's something I'll have to figure out. Maybe you do need one client computer set up and running all of the time to make this a true syncing service. That's where a Raspberry Pi with a huge hard drive come in, right?

So what about hosting your own syncing "service"? It sounds very attractive, and with Syncthing, I can see myself doing it.

Major aside: I recently started thinking about using the Linux desktop more, and that led me back to OpenBSD, which is generally more fun, and good on you if that's a thing you (like me on occasion) associate with computer operating systems. I hesitate to call it a sickness, but I won't say anything if you do. I set up OpenBSD 6.4 on my old HP laptop, where I can easily swap hard drives in and out, and so far it's been fun and educational. I even got the JVM working, so I can develop in Java. I need to try something with JavaFX. If I can get a Java GUI to pop up in OpenBSD, that will be something. My blogPoster Ruby script also works on OpenBSD.

Syncthing is flexible: There are Syncthing packages for all of the BSDs, even Dragonfly, and many Linux architectures, including ARM, MIPS, PowerPC and even s390x.

Answers to some Syncthing questions: Sam Schlinkert has a post that answers some of my questions, including the one on whether setting up a Raspberry Pi can help Syncthing do its thing.