Encrypted email using Thunderbird and OpenPGP (built into Thunderbird). There are some how-to's though I might just write a new one. Header data including recipients will not be encrypted but the message body will.

It is not perfect due to lack of hiding recipients but most people already have email. Some people may need to enable IMAP(S) access in their mail account profile and may need to generate an "app" password for their mail client (Fastmail requires this for example). The big upside is that the keys are generated by the client and the mail server is not involved in that process. Public keys can be shared in person (thumb drive) or over a key server over over email as attachments. In person is the strongest security. Some key servers allow discoverability which may potentially expose people to encrypted malware and spam.