XML file type:The xml file type is blacklisted since MW 1.39 and has to be allowed in LocalSettings.php:
$GLOBALS['wgProhibitedFileExtensions'] = array_diff( $GLOBALS['wgProhibitedFileExtensions'] ?? [], [ 'xml' ] );
$GLOBALS['wgMimeTypeExclusions'] = array_diff( $GLOBALS['wgMimeTypeExclusions'] ?? [], [ 'application/xml', 'text/xml' ] );