probably never the game seems to be using some incredibly old gamemaker version perhaps 8 or 8.1 but I am just guessing based off the text box the splash screen and that everything is in 1 exe
It uses Godot. Godot can export to Linux out of the box. Pretty obvious if you look at the EXE's icon. The only reason it's not on Linux is either the developer forgot or there's some niche incompatibility issues.
