It is not that simple. The engine I'm using is in alpha, it has many bugs on Linux. As a whole, getting games to be stable on Linux is a huge headache. As the sole developer working on it in his free time, I can't spend hours playing the game of "is it me or the engine" with the bugs, especially on a free game.
I want to release the game on Steam Deck but I just don't have the capacity to do that right now. Hopefully in the future :)