how do i make a playit.gg server for gmod
if you just want a server to play with your friends on steam, Gmod already has peer to peer networking so your friends can easily join you by right clicking your profile on the steam friend list. You can also use the Addon Share Mod so that workshop addons you subscribed to will also be automatically downloaded to your friends.
For a dedicated server though, I havent tried it yet but facepunch does have an official guide for creating one. It uses SteamCMD, the same utility used to run other source engine servers. Make sure to set the portforward the tunnel to TCP/UDP 27015, then join the ip via the community server browser
Garry’s mod already has -p2p flag.