The only restriction YouTube has is that you can’t create videos that purely say “go check us out on this other platform”, which is what they used to do for WAN show when it was only streamed on Twitch but announced on YT.
Yeah, I've seen several creators mention "extended" or "uncensored" versions of their content on another platform. Off the top of my head, Corridor Digital is one example that advertises their alternative content pretty heavily.
