HaxeFlixel does export to Linux, but without a Linux machine, it's tough to build and test it. I am looking into getting one at some point between now and the end of development on the game, though.
Linux runs on just about any hardware. Most ports just target Ubuntu and call it good. Not exactly what I want (as I'm wanting an ARM Linux port) but I know my use-case is very niche. Ubuntu doesn't cost anything and runs on typical x86_64 hardware. There's plenty of other great distributions, but if you're just wanting something to test ports on, that's what most Linux users will be expecting it to target.
An ARM version would mainly cover Raspberry Pis and similar hardware. If you want to target that, Pis are pretty cheap, but I don't think anyone will blame you for forgoing those builds. 😅