Noticed when testing other child tickets of T6935:
It's not possible to enter a ldap (or ldaps) keyserver string in the modern format via the Kleopatra settings, as this ist prefixed with hkps://.

Korrekt example string in the dirmngr.conf would be:

keyserver ldap:gnupgkeys.w32demo.g10code.de:::::ntds

without // after the ldap: or ldaps:

Please do not modify the dirmngr.conf entries for the keyserver in those cases.

For the name format of keyserver strings see the manpage of dirmngr (look for --keyserver)