You should broaden your hardware horizons.

Straight out of Linux Foundation, https://www.zephyrproject.org/

There are no Linux kernels on Sony PlayStation nor Nintendo's Switch, or even Microsoft's XBox.

Windows with its 80% market share has no Linux kernel.

Zero Linux kernel running on the ca 15% Apple desktops.

Zero Linux kernels running on iOS and iPadOS.

No Linux kernels on Arduino or ESP32, althought they certainly can run ESP-IDF and FreeRTOS.

And then there are INTEGRITY, vxWorks, QNX, NutXX, FreeBSD, OpenBDS, DragonFly, IBM i, z/OS, ClearPath MCP, OS 2200, ThreadX, SphereOS, Fuchsia,.... and plenty more I won't bother to list, none of them with Linux kernel.

You are right, in the grand scheme of things, Windows is probably only 20% of gaming market share

PlayStation and Roblox have the same MAU as Steam, that says it all

Steam's MAU probably includes people who boot their PC and have steam open in the systray