From the sole developer responsible for Factorio's Linux-native port: https://www.factorio.com/blog/post/fff-408

"Why don't most games support macOS and Linux?" is a sentiment I often see echoed across the internet. Supporting a new platform is a lot more than just changing some flags and hitting compile. Windows, macOS, Linux, and the Nintendo Switch all use different compilers, different implementations of the C++ standard library, and have different implementation quirks, bugs, and features. You need to set up CI for the new platform, expand your build system to support the new compiler(s) and architecture(s), and have at least one person on the team that cares enough about the platform to actively maintain it. If you are a video game, you will likely need to add support for another graphics backend (Vulkan or OpenGL) as well, since DirectX is Windows-exclusive.

Many developers will take one look at the Windows market share and decide that it is not worth the trouble to support other platforms. Also, with the meteoric rise of the Steam Deck and Proton, it is easier than ever for game developers to ignore Linux support because Valve does some black magic that lets their game run anyway.

The list of Linux-first games is so short it's not even a factor. It's very difficult to justify the additional effort of implementing a platform that serves exclusively the playerbase with a ~3% market share, especially when a different method exists to serve that same playerbase that works just as well and also serves the 90%+ with no additional effort.

The article I linked also contains an explanation as to why GNOME's decision to drop server-side decorations is fucking stupid.