I had the same problem in Ubuntu 20.04. I tried to install a hibernation menu using the two extensions bellow:
In Firefox the slider of the button was set to the 'On' state and nothing was happening. After refreshing the page, the button was set again to the 'Off' the state.
After I updated Ubuntu using Software Updater and rebooted the system, I successfully enabled the needed extensions. The following things were required (I do not yet know the exact order and how many times some points should be repeated to take proper effect):
- Pressing the configuration button of the extension.
- Pressing again 'Off' then 'On' for disabling and enabling the extension.
- Pressing Alt+F2, entering
r
and pressing Enter.
- Logging out and logging in.
After that the extensions were added to UI.
For installing GNOME extensions support, I used the instructions from this article: https://www.omgubuntu.co.uk/install-gnome-extensions-on-ubuntu
Here are the relevant steps from it:
Add the "GNOME Shell integration" add-on to the browser (Firefox or Chrome).
Install chrome-gnome-shell
(also suitable for Firefox):
sudo apt install chrome-gnome-shell
Installed Tweaks:
sudo apt install gnome-tweaks
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