CLI for joomla 4 not working for me

Question

Joomla 4

PHP 7.3.1

Composer and NPM node modules installed

Following this doc on Joomladocs, CLI Update, php cli/joomla.php - and whatever command I add after doesn't work. I get an error message (probably from Symfony).

The error message is very descriptive (kidding):

   <div class="container"> 
    <h1>Whoops, looks like something went wrong.
    </h1> 
    </div> 

It comes from this file: /libraries/vendor/symfony/debug/ExceptionHandler.php

While a test file with some php - php cli/test.php - works allright.

What am I doing wrong ?