ERR_EMPTY_RESPONSE during installation with PHP 7.3
Drupal doesn’t officially (or unofficially as far as I’m aware) support PHP 7.3 at time of writing.

You should downgrade to PHP 7.2, and probably consider revising your operating procedures so you don’t end up using pre-release versions of PHP.

If you still see a problem, you probably haven’t configured Apache and mod_php correctly for the new version.