I recently did an “online festival” of several streaming performers. We built an rtmp system with nginx where we’d have people stream to our rtmp address, then retrieve the stream with vlc, and use OBS to interrupt the main stream we have constantly running on youtube (it’s an audiovisual radio channel). The biggest pita is virtual audio routing for performers 90% of the time. The server connection to us was just through OBS on their systems using “custom connection” the rtmp address, and a key we’d provide and switch throughout the festival as different people connected.
Sound check, etc, was also a bit of a pain, but it’s all workable with preparation.