This is the answer. If necessary, you livestream a call run on a separate service (think: a call of 5-20 people on Zoom, where the audio and video/screenshare is piped into YouTube).
consider this. the "host" creates a peertube livestreaming link and sets it as unlisted. that way only people with the link can watch the stream. sure it wont have any moderation but is that possible in a 1000 zoom meeting beyond who can open the mic or share screen?