This is how a platform update is done.
https://youtu.be/Fe5Gk-YvC1U
Take notes STADIA MARKETING.
Especially because the Doom Eternal DLC (which is also stand-alone, btw), which is the first game they mention, is also available on Stadia.
Would be great to see Stadia do an update in this format....even if it's every 15 days or once a month