While it's a bit harder to engage with audiences on multiple platforms, it's definitely possible.
Since the communication direct is still mostly one way, you can e.g. aggregate all the chats from multiple platforms into a single one, and treat it like you would right now. Rocketbeans.tv, a German television-like streaming station that I watch a lot has a "superchat"[0] that does just that (which I think they built in-house), and it works really well. From a quick search, it looks like Restream.io also provides such a tool.
Since the communication direct is still mostly one way, you can e.g. aggregate all the chats from multiple platforms into a single one, and treat it like you would right now. Rocketbeans.tv, a German television-like streaming station that I watch a lot has a "superchat"[0] that does just that (which I think they built in-house), and it works really well. From a quick search, it looks like Restream.io also provides such a tool.
[0]: https://rocketbeans.tv/superchad/