In T8101#213455, @werner wrote:

You need to use a current Windows version (and not Windows Server 2016)

For the time being I "upgraded 5.0.1 to 4.4.1 (in the new directory), and then Kleopatra started again.
When upgrading that installation again to 5.0.1, Kleopatra does not start (same error message as before).

Also: When I click "Abort" ("Abbrechen"), the dialog disappeared, but the main windows does not show any progress: Specifically it does not abort.
I had to press "Abort" ("Abbrechen") in the main window; then the upgrade aborted.
When retrying (and confirming that I don't want to install as Administrator (actually I cannot), the proposed target directory still is "C:\Program Files\Gpg4win".
When locating the previous installation directory (it seems it was a subdirectory of %USERPROFIL%\Downloads) the upgrade succeeded, but Kleopatra fails to start.
It want a bin\Qt6Core.dll, bit in the bin directory there is only a Qt5Corew.dll dated " 14. ‎Juli ‎2023, ‏‎13:23:40".
When retrying the installation/upgrade it announced to upgrade 5.0.1, but then did seemingly nothing (I guess as the version was estimated to "be current").
It seems some "reinstall/repair" option is missing.

For security I had turned off passphrase caching, most likely.
Still repeating identical dialog boxes are very confusing to the user: What the previous passphrase wrong (re-enter), or is the passphrase required for a different purpose now?
Isn't it how phishing works (you have to enter some credentials, but you aren't sure what they are actually used for)?

No, I have no admin rights on that computer: I installed the portable version, too. I saw that the previous version had been uninstalled before installation.
On a different computer I tried to reproduce the situation where GPG4WIN had been installed the standard way. I did not see the effect there. However when upgrading I got a message that the c library could not be written; that was because some Kleopatra windows was still open. After manually closing that, a retry was successful. Other software installers close the application before trying an uninstall or update, however.

In T5780#195277, @ikloecker wrote:

For me the change fixes the problem on Windows. (I haven't checked if there was a problem on Linux/X11, but I have verified that the change also works on Linux/X11.)

Just a note (in case it was not clear enough): I was *not* talking about registering "*.pub" for Kleopatra (currently it launches Microsoft Publisher), but I was talking about the file selector's default input pattern (I had to switch to "all files" to be able to see the file I wanted to import):

I guess I asked for it, because much older "PGP Desktop" had it already (via menu entry):

Maybe it's due to the fact that I used a non-admin installation? Actually I'm also surprised that it worked that way. What kind of debug logs could I supply?

In T5903#176176, @ikloecker wrote:

Please submit a separate feature request for this.

I'm late on the train, but (talking about Kleopatra) there is a menu entry to refresh all keys, but I miss a RMB (right mouse button) context menu for the list of certificates to refresh just the current one (much similar like the feature requested, but "one UI level higher").

OK, I'm sorry, please accept my apologies for not having read the dialog message carefully enough. It seems I ignore the second sentence, replacing it with the omnipresent "Do you want to continue?" in my mind. Maybe the excuse is that it was terribly hot and damp in my office, preventing me from thinking.

Strong objection to close: When answering the question with "no", installation aborts!

I checked it: There was an empty bin/gpgconf.ctl, and there still is.
Trying it again today, I still get error messages most notably about failed self-tests, but surprisingly the window is no longer empty.
Instead it seems to take an eternity (minutes, actually still not finished after three minutes) until the certificate cache is loaded.
Maybe the problem is the "Check Point Endpoint Security" being active on the client. It looks as if it prevents use of Kleopatra.
As I don't have administrator rights ("for security reasons"), I cannot analyze what's actually going on.

Seeing that there are "groups" in Kleopatra, I read the docs, and they suggested that the groups are for addressing multiple recipients.

Well, I think it's a matter of taste what keys a user wants to have in which keyring. Some users want only the keys they actually use.
I think policy or the algorithm should not take the decision away from the user. "Free software for unfree users" doesn't make much sense. Maybe I'm just so old that I still think the computer should do what the user wants it to do, and not the other way around (which seems to be a current trend).