Hi @hannob
that's not a problem. It's a Letsencrypt certificate, so you can download the leaf certificate - https://check-your-website.server-daten.de/?q=tlsseminar2019.space#ct-logs
Created a screenshot:
The tool lists the last certificate (leaf, if found, if not, precertificate). But if it is a Letsencrypt precertificate, it's possible to use the serial number to download the leaf certificate via Letsencrypt.
A few days earlier I've added such a check. That's the red marked link.
The idea - @mnordhoff