The depreciated Muon build of Brave is still in the Ubuntu MATE software boutique. I understand it can be updated as a snap file, but right now it’s still in the main software directory and will probably confuse new users when they see the “no longer supported” message.
Also posting this over in the Ubuntu MATE community
It sounds like Martin Wimpress will be updating several programs in their end, including Brave. I don’t know if you all coordinate or not, but I wasn’t sure which party was involved with the update process.