I recently started using Ubuntu 20.04, and I want to customise date & time format (in Windows I could write it down using a "formatted string" like %YYYY-%MM-%day). I am referring to the clock at the top on the panel.
I've found a gnome shell extension (Format Clock), but it's not compatible with gnome-shell versions >= 3.14, and I have 3.36.2. I would want to customise the format differently from the options available on the list in Region & Language. How could I do that?