With Multicam on iPadOS you're unable to switch out of the app without disconnecting the cameras and the stream. However, if you want to see chat from Facebook, YouTube, Twitch, etc. you still can by using iPadOS's multitasking feature. Simply place the app of your streaming destination (or Safari) in your shortcut bar at the bottom of the screen. Then while in the Multicam app slowly swipe up from the bottom of the screen (away from the center white bar) and drag the app icon to the side of the screen.