Looking at other threads I found the problem in some .lock file in my gnupg directory. One of them was locked by a running process and I was not able to delete. So I opened up task manager and I had dozens of gnupg related processes running. I killed all of them and removed any .lock file.
This way Kleopatra started again but the certificate above (aruba) was not present in the imported ones. And, of course, I'm not going to import it anymore, will use my sixt sense to trust certificates...

The exact file that created the lock is attached

The only action I can do is quit the program telling it to stop the background actvity, but I cannot use it anymore...

Ouch, worse problem here. After closing kleopatra telling it to stop doing whatever it was, I restarted the application and now it's stuck in "Loading certificate cache"

The certificate was defintely missing the tag lines, thanks. I also tried opening the certificate from that page (Windows has no problems without the tag lines) and exporting it explicitly as base64, and the output file is fine.
The problem is that the import now seems to go well, but no certificate is imported at all. I tried several times and the import box just closes after selecting the file.
I tried to close Kleopatra and it says there are ongoing background operations. At least 15 mins passed between the import and the closing tentative.
Actually, it is stuck doing something.

Cureently with the same machine using the old DLL I'm able to work with no problems. I tried several times to switch back to the new DLL and the problem appears immediatly.
If you need some other log I can produce it, just direct me. I used the procedure to enable gpgol logs I found on the forums.