How to install gnome extensions from gnome software?
Solution 1:
The Ubuntu Software Center currently is a Snap. While it is designed to replace the old Software Center, it is currently malfunctioning. At some stage, only Snap packages would be shown. Gnome Shell extensions not being available may be another issue.
As a workaround until issues with the new Ubuntu Software in 20.04 are fixed, you may install the Gnome Software application. You can do so with the terminal command:
sudo apt install gnome-software
Look for the icon labeled "Software" instead of "Ubuntu Software" to start this "classical" version.