Op 15-08-2021 om 18:01 schreef Hans:
Hi all,discovered something. It looks like the keys are still not synced to the mirrors. I changed from ftp.de.debian.org to deb.debian.org, and all is working like a charm. So, I suppose, this issue might be solved. But it would be nice to add a package with the actual keys into the repo. The keys in the package "debian-archive-keyring" are too old (2012.1.1).
They're not. They're 2021.1.1.