Brave is an odd one. They've publicly stated[1] they plan to support parts of Manifest v2 for a handful of popular addons (uBlock Origin included) by making limited patches, but they make no promises.

It seems Shields was their main focus for MV3 mitigation, much like Vivaldi's now native content blocker made for the same reason (though Vivaldi has said[2] they won't be supporting MV2 past the last Chromium build that includes it).

[1] https://brave.com/blog/brave-shields-manifest-v3/

[2] https://vivaldi.com/blog/manifest-v3-update-vivaldi-is-futur...