By the way, your screenshot shows the wrong folder. That's why you didn't see the file that the error message mentions.

Note that the error message may occur a last time when 5.0.2 (or earlier) is updated to a newer version because the uninstaller of 5.0.2 cannot be fixed retroactively.

In general, we don't show the key IDs. User ID + creation date will almost always uniquely identify all keys. (And only the fingerprint truly identifies a key anyway.)

This happens occasionally and is not related to upgrading from 5.0.1 to 5.0.2. It can happen when installing any 5.0.x version (including the betas) over an installed 5.0.x.

Well, I don't think we'll add platform-specific X11 code to pinentry-qt just to check for an invalid DISPLAY. We are using Qt so that we don't have to deal with platform-specific stuff. I have no intention to look into this and, given Wayland, investing any more time in X11 feels wasted. We might accept a patch that can be used by all GUI pinentries to check for a usable DISPLAY.

Maybe. EncryptionResult has a list of invalid recipients and I've changed the code to show the Retry dialog only if there's at least one invalid recipient.

I tried to add the list of invalid recipients to the message box, but it seems that gpgsm stops the validation of the certificates at the first invalid recipient. I got only the first Bob certificate reported as invalid recipient when I tried to encrypt to both Bob certificates so that it doesn't make sense to list the (incomplete) list of invalid recipients. It also means that Kleopatra cannot update the invalid recipient certificates because it knows only of one invalid certificate.

Ideally the certificate would change, but Kleopatra has no idea that this certificate turned out to be not valid. In fact, Kleopatra doesn't even know that the encryption failed because of some certificate. It could have failed for any other reason (e.g. full disk). Kleopatra only knows that an error occurred and offers to retry with lower security. (I looked at GpgOL and it does the same.)

Current implementation for the case of an S/MIME certificate which turns out to be invalid when it's used for encryption. Is that what we want?

Apparently, DISPLAY is hostname:displaynumber.screennumber where hostname and .screennumber are optional and where hostname is a hostname or maybe host/unix. Does hostname include IPv6 address literals? Anyway, I guess the only sensible heuristic is to consider any DISPLAY value that contains : as valid.

How is "invalid DISPLAY" defined? DISPLAY=invalid? Anything that's not DISPLAY=:<some number>? Why do screen and tmux have to use an extra-wurst?

As noted by @ametzler1 pinentry-qt has such a fallback. Of course, we can try to improve the heuristics pinentry-qt uses.

I have added the fix as patch for VSD 3.3 because the commits that introduced this regression were also added as patches for VSD 3.3.

This is a regression that was introduced with T7759: Kleopatra: Notepad encryption with S/MIME fails.

Fixed. For VSD 3.4 this will also be fixed if gpgme is updated.

This is a bug in gpgme. gpgsm_assuan_simple_command only reads a single line before waiting for more data although there is a second line (ERR ...) ready to be read. gpgsm never sends more data because it has already sent its full answer. So gpgme waits forever.