Perhaps you should give Unity a go? All its features are a part of the free version, including Web, Linux, Windows, MacOS, etc. build support. I've been using it for over a year and am very happy with it; I never payed a penny!
I will definitely give Unity a go in the future!! It just seems super daunting to learn a new engine especially Unity since it's a massive engine compare to gamemaker haha but I know basic C# so hopefully it won't HARD!
In the meantime, I'll might able to Linux port for gamemaker next week or so. Either that or I'll try to re-make this with Unity. Either way i'll let you know, but a Linux version is available :D
My two unsolicited cents: I guess a HTML5 port would work on Linux too? It also works on mobile so makes for a cheap iOS/Android port ;)