it doesn’t say if it uses one of their servers
It does not.
if the two devices should be up at the same time
You can’t sync 2 devices when they have no way to connect to each other, so no.
I would recommend getting a server. And by “server” I mean literally any computer with Syncthing installed and left on.
bufalo1973@lemm.ee 4 months ago
I think the “normal” usage is having an always on computer as a server and link all other devices to that one for updates.