I am generally not a fan of theming an app to look like another app/environment/whatever, BUT I am also tired of Firefox on GNOME feeling stuck five years ago visually...
So I am giving https://github.com/rafaelmardojai/firefox-gnome-theme a shot. It's... interesting! I like that it does really look like GNOME Web at a glance and feels more at home in Adwaita, but at the same time, there are clearly issues here and there because it tries to theme EVERYTHING.
I feel like I'd be fine with something that doesn't rearrange things as much but just updates the base window style but leaves everything else alone. But this is pretty nice, too. 🤔
I'll use it for a bit and see how I like it. :)
Also: the installation instructions are deceptively confusing! You can just run the automatic install script, or download it and copy-paste about two lines is all to get it to do the right thing.
@rafaelmardojai I use your theme. I am personally comfortable with his or is now, especially when it comes to theming everything