I use Firefox with uBlock Origin on the Mac and it works great, but for Safari the best option I've found is AdGuard (https://adguard.com). However, it is nowhere near as effective as uBlock Origin since Safari did the Manifest V3 thing.
This was unrelated to Manifest V3, and in fact Safari has not deprecated Manifest V2. Manifest V3 does remove support for webRequest BlockingResponse in Chrome, but I believe not in Firefox.
