Classic GNOME Flashback in Ubuntu 20.04

Solution 1:

You have to try MATE as in Ubuntu MATE. Install it with

sudo apt update
sudo apt install ubuntu-mate-desktop^

then reboot, login to MATE session and enjoy classical traditional desktop without bells and whistles.

Customization is possible by running MATE Tweak after installation - you can switch Panel layout to Traditional layout (as in GNOME 2) -

or try more modern layouts which suite your needs.

Additional note:

• you can make a screenshot with opened context menus by running MATE Screenshot with timeout in interactive mode by mate-screenshot -i command.
• you may want to read Ubuntu MATE Guide to know Ubuntu MATE system.
• you may want to read MATEwiki to know MATE desktop.
• you may want to talk with Ubuntu MATE Community on the corresponding site.