Very happy to learn: https://blog.thunderbird.net/2019/10/thunderbird-enigmail-and-openpgp/

"Today the Thunderbird project is happy to announce that for the future Thunderbird 78 release, planned for summer 2020, we will add built-in functionality for email encryption and digital signatures using the OpenPGP standard. This new functionality will replace the Enigmail add-on, which will continue to be supported until Thunderbird 68 end of life, in the Fall of 2020."