Closing the loop on this: our event went very well, and the livestream mostly worked great bar a Firefox crash losing a few minutes of audio
I wrote up notes on what I learned about livestreaming here https://til.simonwillison.net/youtube/livestreaming
@simon what did you use for connectivity? Venue WiFi or tethered to your iPhone cellular? Any issues with tethering & continuity camera? That’s often the hardest part of remote streaming you can’t know what the connection will be like especially when the place is full of attendees