Bromite is available on F-Droid, and unfortunately Vanadium is only available on GrapheneOS unless you build it yourself.
Vanadium doesn't really have any privacy features that people normally think of (anti-fp, adblocking etc), it's a series of security related patches https://github.com/GrapheneOS/Vanadium/tree/12.1/patches
Bromite does have some features like this https://github.com/bromite/bromite, but we've found in experience the adblocker, is not as comprehensive as uBO, particularly in harder blocking modes https://github.com/gorhill/uBlock/wiki/Blocking-mode:-medium...
That said for Android Firefox doesn't have the same process isolation like we see from chromium browsers.
I still wouldn't bother with Brave on mobile when you've got Bromite though.
Bromite is available on F-Droid, and unfortunately Vanadium is only available on GrapheneOS unless you build it yourself.