If you don't yet have a configure.php file or a database, you must explicitly go to YOURSITE.com/zc_install if you are running PHP8+.

If you go to YOURSITE.com, PHP7 will show the Welcome to Zen Cart page, but PHP 8+ will show a blank page. Fixed in PR #5332

https://github.com/zencart/zencart/pull/5332/files