I'm mulling over whether or not to play with zap.stream , but I'll only do it if I can multicast alongside PeerTube. I had an nginx restreamer back in the day, but it spontaneously broke at some point and I'm not sure how to make it work again.
Zap does appear to have a stream forwarding function that could relay to PeerTube via RTMP but that would put them at the center... failures at ZapStream would knock PeerTube out too, and I don't like that.