To enable automatic theme updates you need to use this filter
Add this filter via a plugin.
The filter callback is passed with objects holding information about the theme that will be auto updated. Therefore you can also enable or disable auto update for specific themes.
Here is example code
if ( $item->slug == 'qnimate-theme' ) ) {
return true; // Always update "qnimate-theme" theme
} else {
return $update; // Else, use the normal API response to decide whether to update or not
}
}
add_filter( 'auto_update_theme', 'auto_update_specific_themes', 10, 2 );