I needed to run Stadia on a Libreboot laptop which runs entirely free software. This includes Chromium, which meeans, that I have to use VP9 codec in Stadia to even make it work. Otherwisee it would not work.
Recently Google started rolling out this new feature to Windows users and apparently it is possible on Android as well. It has been in the Chrome for Android Beta for quite some time. You can follow this tutorial to guide you through the process.
Prerequisites Make sure your Chrome browser is up-to-date (requires at least 74 or Beta 73)
Make sure you are running a recent version of Android (tested on 6, which is pretty old)