User Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/105.0.0.0 Safari/537.36 OPR/91.0.4516.16

Steps to reproduce:

In Account Settings select AddKey under End-To_end Encryption to add an OpenPGP key.
Select Create a New OpenPGP key,
Select Continue.
Choose an Identity from drop-down list, and leave other options at default settings
Click Generate Key.
Click Confirm

Actual results:

Message:
OpenPGP Key generation unexpectedly failed

Expected results:

Key should be generated

Importing an existing key also fails - TB hangs with message:
Importing your OpenPGP keys

Peter, did you ever use the Thunderbird feature "Tools / Import" to import from another Thunderbird profile?

We that this feature causes a settings corruption, which leads to the symptom you're experiencing.

I would like to know if you're affected by this known scenario (because you have used the profile import feature), or if we need to research a potential different reason.

In the following message I explained the background.
https://thunderbird.topicbox.com/groups/e2ee/Tbaff07302322d2f5-M2b0cded1284bd9e7abeb0025

At the end of that message are instructions for manually repairing the corruption.

I don't remember if I imported profile from TB 91 - if so it would have been when first installed TB beta so there have been no existing keys in the TB beta profile.
I followed repair instructions in Kai's message - there was no secring.gpg file, I moved encrypted-openpgp-passphrase.txt.
I could then import my secret and public keys created with gpg.
Successfully sent and received encrypted messages with OpenPGP and S/MIME.