Interestingly, it seems GameMaker Studio 2 can make cross-platform development really quite simple, to the point that the developer said porting to Mac & Linux with GMS2 is "just a few clicks of the mouse".
The especially interesting parts are when they talk about Mac & Linux. As I always thought, people with a Mac tend to hang onto them for quite some time making ports a bit of an issue since they don't often have a powerful GPU:
One frustrating part of developing games for Mac, however, is that despite their high prices, Mac systems tend to be pretty weak from a hardware perspective. I’ve also found that people like to hang on to their same MacBook from 10 years ago and expect games to run perfectly well on it, so this is a good time for me to start optimizing the game to make it run more smoothly on lower-end hardware.
I've heard from a number of developers now that Mac specifications end up being an issue. Linux has the advantage there, since it can be run on practically any system as it's not locked-down. Not only that, but the developer had some kind words about Linux users to share too:
Linux tends to be a lot easier to work with. For obvious reasons, Linux users tend to be some of the most tech-savvy of all our players, so they’re really good at reporting bugs and crashes with a lot of detail. Linux users also tend to run this OS on higher-end systems, so optimization is typically not as big of an issue as it is with Mac devices.
Find the blog post here.