Default Basic User Avatar image when none is found

default-bua-avatar.php

<?php
/**
 * This assumes that Gravatar (or one of it's services is set as the default WP avatar option).
 * Adjust this code and insert your own URL to the default avatar.
 * Add this code to your site by following a guide like - https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */

function my_bua_default_avatar_image( $avatar, $id_or_email ) {

    if ( strpos( $avatar, 'gravatar.com' ) !== false ) {
        $default_avatar = "https://URLTOIMAGE.COM/SOME-PATH/IMAGE.png"; // Change this to the URL for the default AVATAR.

        $avatar = "<img src='$default_avatar' srcset='$default_avatar' alt='default avatar' class='avatar avatar-64 photo' height='64' width='64' loading='lazy' decoding='async'/>";
    }

    return $avatar;
}
add_filter( 'basic_user_avatar', 'my_bua_default_avatar_image', 10, 2 );