Hello !
Hubzilla Support ForumEither I found a bug or something is fishy with my server: after "git clone" the system check page informs me with a red "!" that my PHP version is bad: "PHP version 7.1 or greater is required".
But
php --version
states:
PHP 7.3.3-1 [...] (built: Mar 7 2019 20:22:46) ( NTS )
Anyway the "Next" button was available and everything worked without problems so far, so I guess the warning was a false alarm.