The tutorial is valid for Joomla 3 and Joomla 4.
If you have blank pages in your Joomla install or have an error where you are unable to access the Joomla backend. You can easily enable debug & error reporting via file manager in order to debug the error and fix it further.
First login to your FTP or File manager where you can access and edit files for your Joomla root.
Locate the file configuration.php and start editing (either by downloading or opening the file).
In there, locate the following lines.
public $error_reporting = 'none'; public $debug = '0';
Change these values to:
public $error_reporting = 'maximum'; public $debug = '1';
Upload the modified file back to the server.
This will turn on the debug and error reporting and give you the exact error. Once you do have the exact error. You can look into fixing the same and turn off error reporting and debug after gaining access to the Joomla backend.