The trailer promised online multiplayer but so far, at least for the GOG version, there is no option for it. There is only LAN play or single player Comm-Bat. Is this the case on the Steam version or is this unique to the GOG one? Kind of silly that its not ready to go on launch.

At present Galaxy has no means to sign into playfab, we are currently working with GOG to get this up and running. LAN/Direct IP games do work between Steam and GOG however.

What?!

The GOG version of the recently released Quake II: Enhanced Edition also uses the Krex engine and Microsoft's PlayFab network for multiplayer, and it supports crossplay between GOG, Steam, Microsoft Store/XBOX app, and Epic Games versions of the game in the same hosted sessions/lobbies.

My advice would be to use the Galaxy API to get the user's GOG ID and then use that ID as a custom ID to create an account automatically on PlayFab. See https://learn.microsoft.com/en-us/rest/api/playfab/client/authentication/login-with-custom-id?view=playfab-rest

But, you should really ditch PlayFab and be using Epic's online network (EOS) instead. It's the best cross-play solution, and unlike PlayFab, it is free at any scale. PlayFab is only free for development testing from what I have read.