Modify wp-admin page header ‘viewport’ meta data

There’s a new filter admin_viewport_meta in WordPress 5.5 – https://developer.wordpress.org/reference/functions/wp_admin_viewport_meta/

Now you can change viewport:

function my_meta_viewport() {
    return 'width=980,initial-scale=1.0'; // your value
}
add_action( 'admin_viewport_meta', 'my_meta_viewport' );