Federico Carrone has a team that is working on this: https://twitter.com/federicocarrone/status/1585304643344560128

Trey Del Bonis (who wrote this: https://tr3y.io/articles/crypto/bitcoin-zk-rollups.html) is involved as well.

I'm not aware of anyone else working on it, but I hope to see more join. There are several different ways to build rollups on bitcoin, would be great to see different approaches tried or at least fully researched so we have some hard data about what approach would work best technically and also be most politically feasible.