I don't see a team. Try reaching out to the project leader: https://wimpysworld.io/
... Good luck. 
I think this topic is starting to go in circles, it's already long. As I was digging about, I noticed he hasn't posted here in 2025. With this new year, 2026, I hope we can get official clarity too.
As @ratatoskr said for 24.04, I agree that parting ways with a project is OK. Just seen the mentioned NixCon2023 video, and yes, our project leader had this slide:
I want to migrate friends and family to NixOS; they are not Linux experts.
I would be interested if 2 years since that video if he's closer to that objective, then what's the plan for Ubuntu MATE? Just a month ago, he did a talk about Nix + Ubuntu (Nøughty Linux) which is pretty interesting bridge between the Nix world and Ubuntu.
He's active on the Linux Matters podcast if anyone thinks it's worth hanging out here and asking what the vision is for Ubuntu MATE? Plus, this could be a good podcast discussion topic about Ubuntu flavours in general, since other flavours are struggling with collaborators too. (What would be the best course of action? What's different about the Linux community these days?)