i1.wp.com url problem (Jetpack not installed)

I found the answer to your question.

I’ve created a simple avatar plugin. (I edited and developed the code)

if ( !function_exists( 'get_avatar' ) ) :
    function get_avatar( $id_or_email, $size="0", $default="", $alt = false ) {
    if ( ! get_option('show_avatars') )
        return false;
    static $default_url;
    if ( !isset( $default_url ) )  $default_url="http://example.com/image/my-image.png" ;
    if ( false === $alt)
        $safe_alt="";
    else
        $safe_alt = esc_attr( $alt );
    if ( !is_numeric( $size ) )
        $size="0";
    $avatar = "<img alt="{$safe_alt}" src="https://wordpress.stackexchange.com/questions/315430/{$default_url}" class="avatar avatar-{$size} photo avatar-default" height="{$size}" width="{$size}" />";
    return apply_filters( 'get_avatar', $avatar, $id_or_email, $size, $default, $alt );
}
endif;
function __limit_default_avatars_setting( $default )
{
}
add_filter( 'avatar_defaults', '__limit_default_avatars' );


?>

I chose to take the image directly from the directory.

get_template_directory_uri()

instead

$default_url =

it was logical to use this code. because the other is redirecting to wordpress cdn url. (just like in emoji and svg profiles)