This is https://blog.mozilla.org/addons/2019/10/31/firefox-to-discontinue-sideloaded-extensions/ : in Ubuntu, firefox langpacks are sideloaded (installed in /usr/lib/firefox-addons/extensions/).
This is https:/ /blog.mozilla. org/addons/ 2019/10/ 31/firefox- to-discontinue- sideloaded- extensions/ : in Ubuntu, firefox langpacks are sideloaded (installed in /usr/lib/ firefox- addons/ extensions/ ).