If you reiceive the following error while starting phpmyadmin in your browser:

This page isn’t working
Example.com is currently unable to handle this request.
HTTP ERROR 500

Most probably you have a conflict with your PHP version after upgrading to Ubuntu 20.04. If you have different PHP Versions installed, you need to tell phpmyadmin which Version to use.

Open with your editor:

sudo nano /etc/apache2/conf-available/phpmyyadmin.com

and add the following lines after the alias Tag 

<FilesMatch \.php> # Apache 2.4.10+ can proxy to unix socket
        SetHandler "proxy:unix:/var/run/php/php7.4-fpm.sock|fcgi://localhost/"
    </FilesMatch>

 Restart Apache

sudo service apache2 restart

Now open you phpmyadmin page again.