I can confirm that Kleopatra seems to use the system's locale and not the system language, using English language with Dutch locales myself. The language selection dialog shows the correct languages (en_GB as primary and en_US as fallback) but the interface is Dutch.
Kleopatra 3.1.16 on Windows 10 21H1

@fvogt I've now added a logging category. Thanks for the suggestion.

Yes, I infer that the problem lies in the network-related modules. Because this waiting time is too long, it is probably not a problem of calculation and disk.

Which reminds me that we should add a cronjob feature to dirmngr (which already does some background tasks) so that we can easiliy make use of --no-auto-check-trustdb on Windows.

This could be caused by the periodic automatic update of the Web of Trust information. See --auto-check-trustdb in man gpg.

Let me try, this problem sometimes happens, so it may takes some time to come to a conclusion.
But what I know is that after experiencing slow loading, it will not appear again when it is opened again later.

Is there any change if you enable the keyboxd to store the keys? Put

Yeah, that sounds good to me.

In T5551#148510, @werner wrote:

I would prefer to see a fix/hack in pinentry-qt instead.

I see. Thanks!

To minimize the risk of regressions.

Not to be bothersome, but why? DISPLAY seems like the universal method of selecting a display to put things on, where a lot of applications don't support --display or equivalent, especially now there's no equivalent for wayland. It's especially confusing to me when the keep-display option will pass DISPLAY instead of --display. This would also prevent other such scenarios with 3rd party qt/gtk plugins or alternative pinentry implementations.

I would prefer to see a fix/hack in pinentry-qt instead.

Proposed patch:

--- gnupg-2.2.27.orig/agent/call-pinentry.c
+++ gnupg-2.2.27/agent/call-pinentry.c
@@ -202,13 +202,14 @@

Here is the documentation of the new way of single-threaded execution:
https://www.gnu.org/software/libc/manual/html_node/Single_002dThreaded.html