I've been using makertube.net as a non-posting user for now, and they say they are open for new content creators, though it requires contacting them. I don't know if it is one of those that remain silent, but i've seen quite a bunch of creators on it.

The fifth instance denied my application with, "read the coc and reapply"

Don't know what instance that is specifically, but if their application process is anything like reddthat's lemmy application process, there's probably a bit in there about something specific you're supposed to include in the application so they can weed out bots.

I've gone through a similar experience with two instances. Eventually they both approved. It just took them ages. Of course I needed only one.