SohrabHosseini, not in an easy way. The ATEM Extreme can have individual keys for up to 4 cameras, which you could then send over to a Decklink (or similar device) on your computer, but it is only 1080P maximum. Which for live streaming is great, but for a more polished product, not so much. I use the ATEM because it syncs all the recording media and is a breeze to edit multiple camera angles after recording is finished. For working in Unreal Engine, I either just use one camera directly into the Decklink at 4K, or alternately I could use all the recorded media from the multiple camera angles later. In either of those scenarios I am keying in UE.
Dream world I would have the ATEM Pro 4K and an Ultimatte for each camera being fed into my Decklink, and then into UE. But that is just more $$$. So until then I will keep playing with different options, as most of us are.
Hopefully that makes sense and maybe helps?