Thunderbird unable to access external pgp keys

Since upgrading thunderbird to the latest ubuntu package 1:78.7.1+build1-0ubuntu0.20.04.1 (and thus throwing out enigmail) I cannot use encryption anymore.

The 78 version of thunderbird has replaced enigmail with its own implementation of PGP encryption, and it is still able to decrypt messages accessing the pgp agent.

But the access to gnupg seems to be completely broken. The keyring is completely empty, it does not now any public key and needs to learn from scratch.

Even then, I cannot reply to an encrypted mail with an encrypted (unsigned!) answer, since thunderbird cannot find my key.

To enable PGP functions at all, thunderbird requires to enter the settings and configure which pgp key belongs to the mailbox account, and offers to

* create a new key
* import from a file
* use an external gnupg key (e.g. on smartcard)

Since I'm using a smartcard key, I've chosen the third option and entered the key id, which is accepted, but not listed in the key manager. Even if my own key is technically not required to send an encrypted list (except for making the Sent folder readable for myself), I can't send the message. Thunderbird raises an error message because the configured key cannot be found on the keyring.

Which is technically correct, since the import from gnupg didn't work, both with the smartcard and a regular soft key.

Obviously, thunderbird has some problem accessing the gnupg keys.

My first guess was that apparmor causes problems, but that's not the case. I've used strace to verify that thunderbird has access to ~/.gnupg , and indeed it can and does read the files, therefore I'm not sure, why it actually doesn't work.

Nevertheless, it doesn't work and I currently can't send encrypted messages.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: thunderbird 1:78.7.1+build1-0ubuntu0.20.04.1
ProcVersionSignature: Ubuntu 5.4.0-65.73-generic 5.4.78
Uname: Linux 5.4.0-65-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
AddonCompatCheckDisabled: False
ApportVersion: 2.20.11-0ubuntu27.16
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: hadmut 1759 F.... pulseaudio
 /dev/snd/pcmC0D0p: hadmut 1759 F...m pulseaudio
BuildID: 20210203182138
CasperMD5CheckResult: skip
Channel: Unavailable
CurrentDesktop: LXQt
Date: Thu Feb 25 12:22:09 2021
Extensions: extensions.sqlite corrupt or missing
ForcedLayersAccel: False
IncompatibleExtensions: Unavailable (corrupt or non-existant compatibility.ini or extensions.sqlite)
InstallationDate: Installed on 2020-06-12 (257 days ago)
InstallationMedia: Lubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
Locales: extensions.sqlite corrupt or missing
MostRecentCrashID: bp-42a938ea-d29a-4ad6-95cd-df43e0210213
PrefErrors: Unexpected character ',' before close parenthesis @ /usr/lib/thunderbird/omni.ja:greprefs.js:732
PrefSources: prefs.js
Profiles: Profile0 (Default) - LastVersion=78.7.1/20210203182138 (In use)
RunningIncompatibleAddons: False
SourcePackage: thunderbird
SubmittedCrashIDs:
 bp-42a938ea-d29a-4ad6-95cd-df43e0210213
 bp-cd2c713c-37b0-4b60-9b06-b94130210125
Themes: extensions.sqlite corrupt or missing
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 10/12/2012
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: H61TIW08.111
dmi.board.asset.tag: To be filled by O.E.M.
dmi.board.name: H61H2-TI2
dmi.board.vendor: Medion
dmi.board.version: 1.0
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 3
dmi.chassis.vendor: Medion
dmi.chassis.version: 1.0
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrH61TIW08.111:bd10/12/2012:svnMedion:pnG24:pvr1.0:rvnMedion:rnH61H2-TI2:rvr1.0:cvnMedion:ct3:cvr1.0:
dmi.product.family: To be filled by O.E.M.
dmi.product.name: G24
dmi.product.sku: To be filled by O.E.M.
dmi.product.version: 1.0
dmi.sys.vendor: Medion