A few friends and I picked this up on GOG with the express intent of playing MP.

So far it's been... OK. Getting a game going is smooth and reliable, but once in game we seem to error out frequently with random "X has been disconnected from the lobby". Sometimes there is no notification that anything is wrong for the dropped player, sometimes a red box pops up with "GOG Failure (0x03, 0x00)" which is not particularly helpful for troubleshooting.

Anyone have any MP experiences to share? Any idea if anything MP related is logged on the ES2 or Galaxy logs? It would be great to have stable MP, especially considering that Amplitude is working on The Last Patch which should clean up a bunch of longstanding issues.

Is there steam/gog crossplay?

I don't think so,  but I don't recall seeing any official statement one way or the other.

After reading my friends the riot act and telling them we needed to follow this to the letter:

https://gameplay.tips/guides/9277-endless-space-2.html

All instability aside from the odd desync (easily resolved with save/rejoin) has gone away.   So it seems after all the GOG version is just as stable as the Steam version.