Well, Mull is more like a “Librewolf for Android”, I (think) it is more privacy-focused than Fennec.
Mull also supports more extensions from developer options.
Check these out for Librewolf and Mull’s results. Fennec isn’t in the list (yet?)
https://privacytests.org/
https://privacytests.org/android.html
OpenBoard, Florisboard, AnySoftKeyboard
THERE ARE ALTERNATIVES, PEOPLE!