I am having trouble downloading the Firefox extension on a Lenovo Chromebook, I can download linux do I have to use linux for Firefox browser?
for chrome you can install firefox in 2 ways by using the play store which will download the android version of firefox then you can download the extension from here https://addons.mozilla.org/en-US/android/
or you download firefox using the linux way as in this https://www.androidguys.com/tips-tools/how-to-enable-linux-apps-on-chrome-os/
then you can install the desktop version of firefox on your chrome then install the extension from here
hope that help and have a nice day