or restream FROM Zapstream TO youtube and animate your audience to join the chat on Zapstream (just as one example). Instead, they ignore the ZS chat because they're busy weith their YT, Twitch and X restream chat.

This is quite common already even outside of Nostr. A lot of people stream on multiple platforms, rumble, twitch, yt. Rumble chat seems most ignored on a lot of streams I've seen. But merely mentioning is a good thing to spread the word and all that. Even if it is in a small way. I've never used Entropy for example, but I've heard of it cos people multistreaming often mention it