Edit: I resolved the problem myself. Please see my answer below.
In Kleopatra (Windows), I have the following key server

When I try to fetch the GPG public key of XUbuntu (843938DF228D22F7B3742BC0D94AA3F0EFE21092) using Lookup on Server functionality, Kleopatra doesn't return anything.

I've tried the following servers but nothing changed.
- hkp://keys.gnupg.net
- keys.gnupg.net
- http://gpg-keyserver.de
My Kleopatra version
How should I debug this problem? Is there anything I'm missing here?


