Somehow I'm unable to disable ALL mods. I tried several times and removed the selection of every mod and clicked "apply" and when I check again to see if it worked the mods I just unchecked are selected again and also appear in-game. Most obvious is the minimap Hud. No use for it in Forge but I always have to remove it. I will unsubscribe the mods for now.
Also, when a friend asks me and I join the game via Steam (no invitation!) I'm missing my profile icon and the portrait frame. I always have to leave the game lobby and just click the things again, even though they're still checked. I'm not sure if that's only me or the way I join but generally I don't have the game open, when I'm asked to join, so I right click in the Steam chat-window of the friend and then "join game", which opens DST and then the Lobby of the custom game room.
I just opened a custom game for myself to see if the icon and background are missing but they're both there.