Administration - Installation - Core: Re: Menu and some buttons missing in 6.1 / Docker

I may have just answered my own question.

I just found this thread: 
https://docu.ilias.de/ilias.php?ref_id=1875&cmdClass=ilobjforumgui&thr_pk=6641&cmd=viewThread&cmdNode=wg:2g&baseClass=ilRepositoryGUI

and the answer: PHP 7.4 changed to 7.3. Works!

My 6.0 server is on PHP Version 7.2.31.
The docker 6.1 server is using 7.4.
I will try it with 7.3 instead.