Noticed during testing for 3.1.20. When you clear out the keyserver field in the directory services config and use apply it will set the keyserver to hkps:// instead of the placeholder text hkps://keyserver.ubuntu.com
To reproduce: Open Kleopatra config. Clear out Keyserver. Use Apply / OK. Open the config again or try searching something. It will have hkps:// as keyserver URL configured.