Application tried to create a window, but no driver could be loaded.Make sure that your X server is running and that $DISPLAY is set correctly.
Before v21, there used to be something you could add to the Blockland desktop shortcut to enable the mission editor, i can't remember what it is, but i think it was something like adding -mod editor after the path to the exe file
Alright, I gave up and ran it with xvfb-run. Same outcome. It tried to open a window, but it couldn't.
If you're giving up on tmux, then try my script. It should work.