Which I think is kinda weird decision since they could’ve just hidden a setting that unlocks all addons in the options. But maybe they were so incompatible at the time that it wasn’t worth the headache.
If you use Beta or Nightly, you can turn on dev tools and use a custom addon list from a collection in your user account. https://blog.mozilla.org/addons/2020/09/29/expanded-extension-support-in-firefox-for-android-nightly/