The 500 Internal Server Error is expected with those snippets.

The second one cannot be used in a .htaccess file because DirectoryMatch and AllowOverride are only valid in the Apache server or VirtualHost configuration. Apache will therefore return a 500 error.

The first snippet also shouldn't be added to Joomla's root .htaccess, as it would block the execution of all PHP files, including index.php, effectively breaking both the frontend and backend.

If your goal is to prevent PHP execution in writable directories (images, media, tmp, cache, etc.), the rules must be applied only to those directories, or configured centrally in the Apache configuration.

For an easier setup, you could use Admin Tools Pro's .htaccess Maker or my free HTProtect extension. Both deploy the appropriate protection rules with just one or two clicks, eliminating the need to edit .htaccess files manually or risk breaking your site.

That's definitely not expected. What does the red banner say? Could you please enable Joomla System Debug, try the installation again, and let me know the exact error message?

System → Global Configuration → System → Debug System = Yes

Even the "https://github.com/zkrana/joomla-security-scanner" says:

Hardening The most effective server-level fix is blocking PHP execution in directories that should only ever hold static assets. Add this to your site's .htaccess:

<DirectoryMatch "/(media|images|uploads|tmp|cache|assets|icons|fonts)(/|$)"> AllowOverride None <FilesMatch "(?i).(php|phtml|phar|php[0-9]?|php..*|shtml)$"> Require all denied </FilesMatch> </DirectoryMatch>

also this gives me the 500 error code

I will try a different website... and is exactly the same