Hi @MoD666 thank you very much for all this work. Very appreciated!
I only have an older version but it looks like OptimizePress Dashboard maybe causing the issue and not OptimizeBuilder? It’s possible though that a newer version of OptimizeBuilder may cause this issue. I will try to reach out to them and explain similar to https://wordpress.org/support/topic/php-di-upgrade/
We have been spending quite some time trying to figure out any way to make this work but we couldn’t find any way that will work. I’m hoping they might consider upgrading their PHP-DI library as well as it would be needed for PHP 8 support. I’ll get in touch with them now and otherwise there is very unfortunately only the option to either disable Matomo or the other plugin. Sorry about that and if they get back to me I will let you know.