I once set up https://laminar.ohwg.net/
It has the special quirks that it's configured outside the repository and script based. Listening for webhooks from forgejo needs an additional service though. (Like https://github.com/adnanh/webhook)
Demo: https://ci.ohwg.net/
Maybe give https://vdo.ninja/?screenshare=&quality=0 a try? That's also completely WebRTC direct connection based. Saved as a bookmark it's simple to spin up a stream, so the chat decision is disconnected from the streaming.