it just uses your local wifi. run it on your machines, tell them to trust each other, and you're set. and if you manage to edit the same file at once, it handles the conflict and saves both copies.
for anyone who just wants to get files from point a to b without the headache. hope it makes your life a bit less annoying.
github: https://github.com/sirbread/sink binary: https://github.com/sirbread/sink/releases/tag/v0.1
It does have GUI, which I use. I wouldn't call it pretty or polished, but it works and I understand how it works and the way it works is exactly how I think syncing should work.
I've also configured it to run a GUI diff tool diffuse to easily combine changes in case of conflicts (when a file was changed on both sides since the last sync).
I wish it was a bit more modern and re-written in a modern language, but that's secondary qualities for a program.