Better way (shows site icon from customizer if existent): https://gist.github.com/webdados/a7702e588070f9a1cfa12dff89b3573c

restore-favicon-handling.php

<?php
/**
 * Do not show favicon (prevents WP logo from showing up since WP 5.4).
 * Does NOT show a maybe-existent site icon instead. For that, look here: https://gist.github.com/webdados/a7702e588070f9a1cfa12dff89b3573c
 */
add_action( 'do_faviconico', function() {
	header( 'Content-Type: image/vnd.microsoft.icon' );
	exit;
} );

This kills the customizer icon.

I think this might be a better solution: https://gist.github.com/webdados/a7702e588070f9a1cfa12dff89b3573c

Yes, you are right. Will update the code with a link to your Gist

👍