#1390 (comment)
composer-normalize seems to throw a false error: 'Your Composer dependencies require a PHP version ">= 7.4.0"'.
The message is misleading, since we install composer-normalize via PHIVE. composer-normalize does not follow semver: version 2.21.0 dropped support for PHP 7.3, which is why the error occurs.
Adjusting the require-dev section of composer.json to require PHP >= 7.4 would not be viable, since that would prevent running the unit tests on 7.3. But an explanatory note in the contributing guidlines would probably not go amiss...
#1390 (comment)