Before Nova, there was Firefox Proton, an update focusing on removing visual clutter with simplified menus back in June 2021 alongside Firefox 89. Going back even further, we saw the 2017 “Photon” redesign land with Firefox 57.
(The design that landed alongside the Quantum update was called “Photon”.)
From the article:
(The design that landed alongside the Quantum update was called “Photon”.)