Ubuntu Single Sign-On Account stuck on "Connecting..."

Try removing any existing Ubuntu accounts and adding them again. That simple step worked for me.

You should be getting a message about authorising the snap daemon (which asks for your local root user password). If not, check if snap works:

snap login

If you don't have snap, there might be something wrong with your Ubuntu (it should be included by default). Snap can, however, be installed:

sudo apt install snapd

If you still cannot add your account, but you only wanted to enable canonical-livepatch, try activating it from terminal:

sudo snap install canonical-livepatch
sudo canonical-livepatch enable <key>

replace < key > with your live-patch key, which can be generated from:
https://www.ubuntu.com/livepatch

Then go open 'software & updates', click on the 'updates' tab, and enable livepatch

With 20.04, I found that the livepatch URL above redirects to Ubuntu Advantage and that when you click the green button "Get Ubuntu Advantage" then you can create a free key but the command to enable livepatch is different:

sudo ua attach <key>