I had a period where I was on a team like that. We didn't have a manager.

Though some of my worst work periods was when I didn't have a manager either lol.

I'm reminded of the story of Graphing Calculator:

"His contract in another division at Apple had just ended, so he told his manager that he would start reporting to me. She didn't ask who I was and let him keep his office and badge. In turn, I told people that I was reporting to him. Since that left no managers in the loop, we had no meetings and could be extremely productive."

- https://www.pacifict.com/story/

It’s almost as if the roles/titles aren’t the determining factor.