Multiple channels in a single RSS xml - is it ever appropriate?

Question

A typical xml file for an RSS feed starts with an \"rss\" element on the outermost level, and usually has a single \"channel\" element within it that represents the \"feed\"

Answer 1

From here:

Subordinate to the <rss> element is a single <channel> element, which contains information about the channel (metadata) and its contents.

So there not only is no use case for that – it isn't even allowed.