Why Gnome Extensions isn’t all set up and configured by default on Ubuntu at this point is a bit beyond me. There are some awesome and borderline critical things available there that are hard to get in any other way. Seriously, who does without a clipboard manager these days?
Gnome Tweaks is an oft recommended tool, and it lets you manage extensions, but not install them. If you go to the Gnome home page you would have to really dig to know that extensions were even a thing at all. You won’t find any of these if you look in the Ubuntu Software Store. No clues whatsoever on the default Ubuntu installation on how to install and manage extensions much less that they are even a thing. I wonder if this is any different in Fedora?
Some of these extensions are great. Ubuntu even utilizes them already under the hood to do things like desktop icons and to customize the dock, so it isn’t as though they are thing to be avoided.
Again, the level of polish on the linux desktop on the whole at this point is really good generally speaking - I was a bit amazed at just how easy and slick it was to set up my VPN and configure the network printer at my office for example - so it is odd that the way to install and manage these nifty little extensions still involves such obscure steps.
Anyway, to get to the point where you can install the extensions:
at CLI
sudo apt install chrome-gnome-shell
This has noting to do with Google Chrome, it just allows browser extensions to reach out of their sandbox to install and manage these extensions in gnome.
Then you will need the web extension called Gnome-shell-integration. https://addons.mozilla.org/en-US/firefox/addon/gnome-shell-integration/
Once those are in place you can go to Gnome Extensions and get the party started
Here are a few of my must haves:
And a few I use more occasionally: