I'll freely admit I'm not always the most up-to-date on things (I'm still running slade 3.2.5 and i guess 3.2.7 came out about four months ago...), and once again, I missed something very important; but I didn't want to post this yesterday (for obvious reasons).
Rarity vs The Changelings now has a post on Equestria Gaming!
They've even put the files together to make it easier to download and play. It's more focused on Custom Edition because it's playable with modern gzdoom, and honestly is a work of art in its own right (I still haven't figured out how the magical beams work, and it impresses me every time).
That said, if you want a more vanilla raridoom experience that still works with gzdoom, keep watching this spot 😁.
Also I threw the Nintendo Hard difficulty in there as a joke. It's like four lines of code and I never made it past map 3. But apparently it's doable, so check that out, too.