I found this: https://exhibitplay.com/game-worker-cooperatives/
Which seems to be all of them.

A thing to note, in my opinion, is that most indie game companies are very small, meaning their employees have a larger say in things by nature. I think registering as a coop is just formalizing what is already the case for a lot of them (though it does also prevent the owners from becoming power hungry/greedy)

They haven't released anything yet but I think Summer Eternal might qualify.

https://www.reddit.com/r/gamedev/s/ARLz1bDORO

Looks like there are several French game studios that are run-like co-ops, including the two different studios that made night in the woods and dead cells.