I am installing Gwent right now.Are there any other games on GOG that have multiplayer routed trough Galaxy?
I am not asking about multiplayer games in general.I know that many games on GOG can have multiplayer routed trough hamachi/game ranger.I am asking about those who don't need any additional software but Galaxy.

If you mean ones that have multiplayer, there are loads... some don't need other software, but aren't routed through Galaxy either - they just go through a server as part of the games built in multiplayer function. You just gotta look for something like S.T.A.L.K.E.R, it doesn't need other software, but isn't through Galaxy

Well, quite a lot of games support multiplayer... its just about finding the ones that don't have to use the third party software. I've never come across a game that needs any extra software. It's usually (well, for me at least) built into the game, like stalker, or, you may have TCP/IP games. This is where you directly connect to a friend through typing their IP address (like the oldies!)