They are deprecating the underlying technology(called manifest V2 or MV2 for short) and replacing it with a different one(MV3) that lacks some of the capabilities for some kind of adblocking.
So yeah, it’s pretty much dead on chromium. The developers of brave have commited to provide a best effort support for their browser though: brave.com/blog/brave-shields-manifest-v3/
Firefox on the other end has no intention of deprecating support for MV2 so any browsers based on that are fine. Keep in mind MV3 supports some adblocking and some Adblockers have already moved to it, it’s just a lesser extent.