With Hangouts on Air dying, there really is no equivalent, easy way to do a live streamed group video chat. Google’s shutdown message points people to YouTube.com/webcam, but that page is only for a single person on a local webcam, not a group video chat. Rolling your own Hangouts on Air replacement would probably involve connecting multiple programs and services together. Skype can record calls but won’t livestream them natively, for instance, so you’d need to pipe your calling software into some kind of livestream program like OBS, and from there you could hook it up to a Twitch or YouTube broadcast. That might be a normal workflow for live streaming pros, but it’s a lot more complicated than just a few clicks on YouTube.com done entirely in a browser.
Google hasn’t given an exact date for the shutdown or said if it plans to replicate group video calls through some other app.