I actually don't even know that game, but if you would love to see it on Stadia, here are two options you can go with:
- First of all contact the developer of the game. If they have plans to bring the game on Stadia or even when they bring it on Stadia or if it's not planned at all. If the developer for example doesn't intent to launch it on this platform, most likely you will not see it here because they would need to get in touch with the Stadia team.
- You can also leave feedback for the Stadia developers and tell them you would love to see Biomutant on the platform (click your profile picture in the top right corner on stadia.google.com or in the Stadia app and select "Feedback").