How to exclude Mail-Adresses from Directory Search?

Hello, is there currently a way to exclude Mail-Addresses from the member directory search?

I tried the following plugin, which should exclude them by default, but it seems not to work (anymore?), because I can still find users with their Mail in my member directory:

https://github.com/MissVeronica/um-reduced-member-directory-search

The plugin does not seem to have an effect.

Then I tried to use the filter from the documentation. I added it to my function.php:

function um_061522_pre_users_query( $obj, $directory_data, $sortby ){

    if( $obj->is_search == true &&  ! empty( $_POST['search'] ) ){
        
        if( ! empty( $obj->where_clauses ) ){
            foreach( $obj->where_clauses as $k => $w ){
                if( strpos( $w, 'umm_search' ) > -1 ){
                    $w = explode(" OR ", $w );
                    $obj->where_clauses[ $k ] = str_replace("( umm_search.um_value = ", "( umm_search.um_key = 'display_name' AND umm_search.um_value LIKE ", $w[0] . '%' ) . ')';
                }
            }
        }
    }
}
add_action("um_pre_users_query","um_061522_pre_users_query", 10, 3 );

If I understand it right, with my code it should just search only in the username. But with the code I always get 0 results…

Any idea?