Neither Safari nor DuckDuckGo—the two other major non-Chromium browsers out there—support uBlock Origin.
DDG's browser is using webview, meaning it uses chrome on Windows/Android. Also not what I would consider a major browser.
Even if Firefox drops support, it's doubtful that many of its major forks will drop support.
For those who want to use something other than a Firefox fork, there are some options.
- Brave has built in ad blocking, but you need to disable a lot of their crap. There are scripts out there that can do it quickly.
- Helium is in beta, but it bundles uBO.
- Orion is currently only available for macOS, but it has a beta for for Linux available. It can install extensions from both Chrome and Firefox.