@Hopp-Art - Microsoft live events can be setup to be viewed in Yammer, Teams, or in Stream, depending on where you initiate the creation of the live event from.
In terms of chat or conversations from the live event you'll want to use have your viewers in either Yammer or Teams to accomplish this.
If you create your live event from Yammer then the live event has the full Yammer conversation ability directly under the live event.
If you create your live event from Teams then you can choose to enable a "Moderated Q&A" option for the live event which allows the event producers to see questions that come in from viewers and choose to allow those questions to be posted to everyone or just answer back privately.
https://docs.microsoft.com/stream/live-event-m365
Stream itself for live events won't have any live chat/conversation at this point.
