Linux
Linux is a suite of open source operating systems. It isn't a single product, but instead a base for creating custom OS's, called distributions. Recently, it has been growing in popularity among gamers due to devices such as the Steam Deck.
It is possible to run games built for Windows on Linux using compatibility layers such as Proton, which is built into Steam. This however can decrease performance, making native builds a more preferable option.
Development support
Currently, developing games on Linux is only partially supported. It's not possible to run Game Studio (the editor) on Linux, even when using a compatibility layer, such as Wine.
However, it is still possible to code and build games natively, meaning that when in a team, some programmers could work on a project using Linux for tasks that don't require the editor.
Note
Game Studio is being rewritten to be cross-platform.
Alternatively, it is possible to create Stride games on Linux using a code-only approach, removing the need for an editor all together.
General support
Starting with 4.4, Linux is no longer in an experimental state. All engine features are fully supported on it.
Aside from Windows, Linux is one of the most actively maintained platforms, due to many contributors using it on a daily basis. Still, if you want to make sure that all engine features continue being supported on Linux, consider becoming a contributor.
Wayland
Wayland is a communication protocol between a display server and it's applications, that has gained popularity among many Linux desktop environments. Many apps however are still yet to adopt it, relying on the outdated X Windowing System (X11). They can work on Wayland compositors thanks to a compatibility layer "Xwayland", but can't utilize modern features that aren't present on X11 (such as fractional scalling).
Currently, games made with Stride can only run using the X windowing system, which is a standard among many games.