>TV has been doing popup ads for years and I am quite sure many Android games also do it. Then you have ads that could be directly embedded into the game play or the games environment itself, a port to Stadia was necessary anyway, so adding ad support could have been done as part of that.

A fair point, and one I hadn't really considered.

I was thinking along the lines of multiplayer FPS games and the like. If you stop play to show some players ads, they'll be dead/have lost by the time the ad is over. If you stop play for all players to show them ads, I'd expect really high loads on servers as they "customize" the ads by region and PII.

Alternatively (as you imply), using "product placement" ads in-game without interrupting game play, I suppose that could work, no matter how disgusting it might be.