Lepton (https://github.com/black7375/Firefox-UI-Fix) to the rescue. I really hope they, or someone else, will allow us to tweak the interface and come back to what we need on our productivity oriented devices, aka computers.
I've been using Vivaldi lately. It's nice but I miss some shortcuts from firefox, and it's still Google Behind.
I feel betrayed by Firefox and depressed about the internet to come a little bit more every day.