error 1: https://magento.stackexchange.com/questions/311806/installation-at-51-module-magento-theme-error-in-magento-2 solution: private function validateURLScheme ( string $filename ) : bool { $allowed_schemes = [ 'ftp' , 'ftps' , 'http' , 'https' ]; $url = parse_url ( $filename ); if ( $url && isset ( $url [ 'scheme' ]) && ! in_array ( $url [ 'scheme' ], $allowed_schemes ) && ! file_exists ( $filename )) { return false ; } return true ; } error 2: Refused to execute script from '<URL>' because its MIME type ('text/html') is not executable, and strict MIME type checking is enabled. require.js:166 Uncaught Error: Script error for: mage/backend/bootstrap require.js:166 Uncaught Error: Script error for: js/theme require.js:166 Uncaught Error: Script error for: jquery require.js:166 Uncaught Error: Script error for: mage/a