Change Profile Username with Fullname

yzc_change_profile_username_to_fullname.php

<?php
/**
 * Change Profile Username with Fullname.
 */
function yzc_change_profile_username_to_fullname( $member_name ) {

    if ( ! bp_is_user() ) {
        return $member_name;
    }

    // Get User Id.
    $user_id = bp_displayed_user_id();

    if ( $user_id == 0 ) {
        return $member_name;
    }
    // Get User Data.
    $user = get_userdata( $user_id );
    
    // Get User Full Name.
    $fullname = $user->user_firstname . ' ' . $user->user_lastname;
    
    if ( empty( $fullname ) ) {
        $fullname = $member_name;
    }
    
    return $fullname;

}

add_filter( 'yz_user_profile_username' , 'yzc_change_profile_username_to_fullname' );