I'm trying to set up Thunderbird (version 91.3.2) with email encryption and an existing GPG key on a smartcard. I have followed [https://wiki.mozilla.org/Thunderbird:OpenPGP:Smartcards#Configure_an_email_account_to_use_an_external_GnuPG_key the corresponding article on wiki.mozilla.org] to set up the encryption in Thunderbird, but trying to decrypt an encrypted email only shows a red banner: "The secret key that is required to decrypt this message is not available.". If I try to send an encrypted message, I simply get an error message: "Sending of the message failed.". I have double and triple checked whether the manually set up key ID matches the one in GPG, and it does. I have tried to use either the parent key ID, or the encryption subkey ID, but to no avail. I have started thunderbird with an environment variable set: GPGME_DEBUG=9:/dev/stdout In fact, requests to encrypt and decrypt emails are sent to GPG, but (between lots of noise) there are error messages: If I try to encrypt an email, I get "GPGME 20211215T175951 5A67E gpgme_get_key:1374: error: End of file <GPGME>". If I try to decrypt an email, I get "GPGME 20211215T180601 5DA8A gpgme_op_decrypt_ext:182: error: Not supported <GPGME>". These error messages seem to indicate that GPGME is in fact unable to find the corresponding key in its keyring - but if I use `gpg --list-secret-keys`, the key is there. I can even save the email in thunderbird, and decrypt it manually from the commandline, so the gpg setup on my system seems to be fine, but there seems to be some disconnect between thunderbird and the GPG keyring on my system. Any idea what I might have configured wrong here?