http://forums.dds6qkxpwdeubwucdiaord2xgbbeyds25rbsgr73tbfpqpt4a6vjwsyd.onion/t/thunderbird-78-deprecates-enigmail/10166
Evolution - very heavy, but the closest TB alternative. Cannot use a key with an email ID different than the one that is signed in. Even if the email address was added to the GPG key? This is a problem for people who migrated email addresses.