the most useful extensions for android firefox - ublock origin, there is already (and many more). Also, mozilla is working on bringing all desktop add-ons to mobile and everyone can contribute.

https://blog.mozilla.org/addons/2023/09/27/test-firefox-android-extensions-and-help-developers-prepare-for-an-open-mobile-ecosystem-in-december/

https://blog.mozilla.org/addons/2020/09/29/expanded-extension-support-in-firefox-for-android-nightly/