Got a Steam Deck too :) but I also run Debian on my main computer since 3 years now.
I know is not available on Unity yet but they are working to add WebGPU which is more efficient than WebGL and it will eventually be replace by WebGPU in near futur. Take a look here if you are interested: https://forum.unity.com/threads/how-about-webgpu.1277615/
Regarding Android, even if it use a linux kernel as it's base, this is another kind of OS.