I am a Nebula subscriber, and highly recommend it. 90% of the stuff that's on Nebula is also on Youtube, but nebula doesn't have the ads. There's a bunch of creators who post Nebula first, an there's a number of "Nebula Exclusives", but by and by, if you look at who the creators are on Nebula (which you can do without signing in by following this link you'll see names that you recognise, or can look up on YouTube to get an idea of what they are like. It does mostly focus on educational and scientific content, as far as I can tell. The exclusives are more content from the same creators.

I wouldn't categorise Nebula as specifically more queer positive. It doesn't have comments, which helps reduce the number of trolls, and a number of the creators are openly queer, the same way they are on YouTube. I suspect they have an internal code of conduct that specifically prohibits homophobia and transphobia, but if they have it's not widely advertised.

You may have the impression it's queer positive because recently Abigail Thorn put up a recording of their play The Prince on Nebula, and that has been widely publicised. I have watched it, and enjoyed it.

As an aside, Nebula's main comments are on r/nebula. I wonder if they're considering setting up a lemmy instance themselves.