Here is the relevant Discourse discussion:

https://discourse.mozilla.org/t/add-on-support-in-new-firefo...

and the relevant GitHub issue, which was locked due to too many people complaining:

https://github.com/mozilla-mobile/fenix/issues/11308

which was closed and moved into this issue, which was locked immediately as this change is... rather unpopular, as is their proposed solution:

https://github.com/mozilla-mobile/fenix/issues/14034