From the new terms:
When you upload or input information through Firefox, you hereby grant us a nonexclusive, royalty-free, worldwide license to use that information to help you navigate, experience, and interact with online content as you indicate with your use of Firefox.
On desktop, it’s easy: Zen Browser, Qutebrowser, Mullvad Browser…etc.
It is the mobile one that is difficult. Literally everything non Chrome sucks.