So I am trying a fresh install of 7.11.9. I get this error on the second page:
Currently we are not able to locate the GD library, as a result you will not be able to use the CSS Sprite functionality.
PHP Version 7.2.24-1+ubuntu18.04.1+deb.sury.org+1
Location of your PHP configuration file (php.ini): /etc/php/7.2/apache2/php.ini
This seems, to me, that this should be fine.
Maybe there is something missing in the php.ini file but I can’t find it if it is.