As weird as this may sound.. I just downloaded the most current version of Processwire on the website, and did a local install with PHP Version 7.4.12 on my Macbook.
I did get te same notice as an user had in 2019: Notice: Trying to access array offset on value of type int in /Users/USERNAME/Sites/www/sites/shop/wire/core/WireDatabasePDOStatement.php on line 107