Last time I saw this pop up, someone suggested using enigma to convert the gmk to gmx, and from there you can convert it in gms2. A lot of stuff is going to break though I'm sure. I've never used the program so I'm not sure how the process works, but heres the link that got posted last time
Installing is as simple as running a few commands in the terminal. I'm not sure how making an official port would help the situation but I might consider it after I manage to get enigma working without needing to delete FreeBSD's make
executable / replacing it with gmake. That would ruin a lot of people's systems if the rely on the original make executable that gmake is not acceptable for, so backing it up is advised. https://enigma-dev.org/docs/Wiki/Install:FreeBSD
Try enigma, it's a free game maker alternative that supports opening GMK files and many of game maker functions, including the use of DLL. Even if it can't run your game, you can still extract all the game resources (sprites, scripts, ...) from the gmk file.
At least in GM8 internal and built-in variables were still treated internally as 32 bit signed integers. Aren't double precision floats generally 64bit?
more (unofficial) documentation
also not sure if related but some stuff in Game Maker (like array depth) is capped at 32000.
While it doesn't run natively, you can try running it in a VM. You can also give ENIGMA a try (though I've never used it and have heard mixed things).
Alternatively, you can try Godot which runs natively in Ubuntu.
I admittedly haven't used Enigma/LateralGM that much (maybe just a couple of times) but I took a look at the dependencies for their various runtimes and Java seems to pop out in all of them, but again, I might be wrong.
Still, even if Enigma's runner didn't need Java then there will still be the issue that it only supports Game Maker 8 projects and earlier. Sure, with the source code in hand it could be possible to rebuild the game into an Enigma-compatible GMK, but if Toby used one or more GMS-only function then it might be a pain to do so...