We tried that, but had to go as low as 0.1 to not get dropped from the game and that makes it unplayable. I suspect it is a network issues, because I can play fine and with game.speed = 1 when I join my friend, when he hosts it.

Hello,
I am running a Factorio server on my Linux server. Everybody that joins the server has a huge Wait for Update (300ms) and has huge FPS/UPS problems.
My Pc is connected via Gigabit LAN with the server and I still have those problems. Everything else running on the server is working flawlessly ...