The article refers to the iPhone app’s ”recent” release, which was 10 years ago.
It actually doesn’t run in the original Doom engine. It’s a “limit removing” WAD, meaning it doesn’t use any additional features but removes static limits: https://doomwiki.org/wiki/Static_limits
I’ve been using Mlem and it’s really good. Everyone else has mentioned Voyager so I’m gonna give that a try too.