Mozilla and the Thunderbird email client development team released version 78.2.1 on the fixed channel last night. Existing Thunderbird installations will be automatically upgraded to the new version, provided that the auto-update feature is not turned off and you have the version 78.x.
One of the big new features of the Thunderbird 78 was the support for PGP encryption built right into the app. Thunderbird users previously had to install extensions like Enigmail to have PGP support. 
The Thunderbird 78 release had built-in support for OpenPGP, but it was not enabled by defaultchoice due to some issues that needed to be resolved.
The Thunderbird 78.2.1 release enables OpenPGP support by default in Thunderbird. Select Tools > OpenPGP Key Managers and you'll see available keys that were previously generated or imported and options to generate new keys that can be used to encrypt your email conversations.
Clicking Generate> New Key Pair starts the process. All you have to do is select one of your available email accounts and click on "create key" to create an encryption key.
