A lot of people are switching to Zen Browser, which essentially is a heavily modified, extremely moddable/themable and UX driven Firefox:
Zen really becomes particularly awesome if you run Linux with a alternative Wayland compositor like Sway, Hyprland, Mango, Wayfire and friends due to the window management in those environments. As a example: https://www.reddit.com/r/zen_browser/comments/1ky8rdp/arch_h... (this particular Zen instance is modded to be transparent, by the way)