After the complete reinstallation of my system (host + VMs), I could not use any key management tool (import, export, create…) in Whonix workstation, both from the command line (gpg) or the GUI (KGpg or OpenPGP).
Consistent error: ‘/home/user/.gnupg/trustdb.gpg: invalid trustdb’. The file was empty.
The workaround was to install enigmail in the host and create a key. The .gnupg folder was created and copied in the VM.