Bernhard Reiter added the comment:
> @pefu:
> Yes, the TLS certificate is a known remaining problem.
> (See msg6639. I've also tried to inform users with my email.)

Sorry. I should have read the other comments more carefully 
before posting.

> Thanks for your note, it is good to know that people care for the wiki!

BTW: I found the following article about using 
wildcard certificates with letsencrypt a helpful read:
http://strugglers.net/~andy/blog/2018/03/19/lets-encrypt-wildcard-certificates-acme-sh-and-automated-dns-verification/
I understand however that this article does not apply to the 
situation here of the roundup moinmoin wiki service.

Liebe Grüße, Peter Funk