Syncthing would be worth checking out. It seems like a good match for what you're mentioning, it automatically handles the networking and file change watching. I've used it in the past to back up photos from phones, and have a few notes on usage.

For syncing two devices with intermittent connectivity (phone and laptop) you really want a third device (raspberry pi in my case) that's always online to act as a buffer and keep each end up to date. I also had some issues with device discovery taking a while though I'm fairly sure it was phone power saving settings that was messing it up. It's stable and popular software, definitely battle tested on Linux, though there are apps for all platforms.

https://syncthing.net/