What happened with unsaturated type families?

There was a project by @kcsongor and @rae, GHC proposal 242. Was anything ever merged from it? Is anyone working on it?

I have been using a custom built GHC 8.11.0 that supports this feature for some time, but it is becoming impractical. I still want to have this feature. If no one is ambitious this way, I should like to merge it myself.

Status (May 2024): Yitang working on it at git@gitlab.haskell.org:mmzk1526/ghc.git, branch mul-dev.