What browser extensions? Why would I want websites to integrate with gnome or kde? What does that even mean?

Isn’t this bad boy installed by default in most Gnome distros? https://chromewebstore.google.com/detail/gnome-shell-integra...

I'm guessing the poster meant the USB and Bluetooth browser protocols (which I still find insane how anyone thought those were a good idea, but it's literally the only way to configure some keyboards today).

Those are not extensions. Not can you use them to talk to dbus.