When the streamer manually starts an ad, then fine, let the ad run immediately (as the streamer is timing it with their content and are aware people can't hear)

But when it comes to auto ads...
Pop up in chat for viewers that you have an ad for viewing, and you have like 5 minutes to trigger it when it suits you, the viewer. For example letting the streamer finish their sentence or their round or race, then start the ad when it fits the viewing.

Full screen, muting the stream. But less obtrusive when the user can choose when it runs.

If the 5 minutes runs out without the user starting the ad, the ad runs.