Incorrect PHP version: 7.3.33 (70333)

Current osCommerce version requires at least PHP 7.4.0

If you've already selected minimal PHP version for your site and still see this message:
Probably you host sets PHP version into root .htaccess file
After the first step of this installation .htaccess has been overwritten and PHP version has been reset to default.
The solution is to change PHP version again or (for advanced users) manually add PHP selector to root .htaccess. Usually it's something like:

<IfModule mime_module>
AddHandler application/x-httpd-ea-php80 .php .php8 .phtml
</IfModule>