CI 4 Showing Blank Pages in ubuntu 20.04 LTS

Did you set the CI environment?
You can do this ether in public/.htaccess

Code:

SetEnv CI_ENVIRONMENT development

 
Or in apaches virtual host file (example below):

PHP Code:

<VirtualHost *:80>
        ServerName MYHOST.MYNETWORK
        DocumentRoot "PATH_TO_CI4/public"
        ErrorLog "/var/log/apache2/MYHOST_error.log"
        CustomLog "/var/log/apache2/MYHOST_access.log" common
        #ServerAlias www.MYHOST.example.com

        SetEnv CI_ENVIRONMENT development

        <Directory "PATH_TO_CI4/public">
            Require all granted
        </Directory>
</VirtualHost> 


Make sure that mod_php is enabled on Ubuntu:

Code:

a2enmod php
sudo systemctl restart apache2