I’ve been told about Mull and fennec, but what about:
(From what I understand)
- Firefox Focus: blocks trackers and erases browsing history
- Firefox Nightly: new updates every night
- Firefox Klar: german version of focus
- Iceraven Browser: 3rd party fork with more add ons
Worth noting that “Focus” is the name of a well known weekly print magazine/news website here. They may just want to avoid a false association.