I had Ubuntu MATE 18.04, and I could change keys like "Ctrl is mapped to Win and usual Ctrl keys", or "Alt is mapped to Right Win...", those options for me were very useful, that let me adapt keyboards of different laptops to have similar functionality.
This was an example in Ubuntu 18.04, MATE desktop:
Now I have Ubuntu 20.04 with GNOME desktop, but I can't find any system-options to configure these "keyboard keys distribution".
Is there any way to change it in GNOME desktop?
An advanced option like this is not available in the pre-installed Settings application, you need to use (GNOME) Tweaks. First install it by running the following command in Terminal (you would have to enable the universe repo first if it's disabled):
Then launch it and you would find the option under Keyboard & Mouse > Additional Layout Options: