Can't find a replacement...if Firefox trying to get rid of all of us that need the larger fonts for the interface..all of a sudden it just disappeared...WAH! Firefox, we need this..please get it together...I'd hate to have to go elsewhere after all this time...old mac user

This is the only add-on / plugin for Firefox that makes it accessible for larger displays and old eyesight! :-)
Sure hope you can get it working with Firefox 57+, I know you are trying...
Thank you!