Of you meet a fellow bitcoiner you trust IRL, exchange about 6 random words on a paper,... you won't have any better key exchange ever, and you don't need to publicly centrally 'share' email addresses or pubkeys.

Give each other a nickname/tag 'John316' or 'MaryXc55' and so you can teach eachother across any platform using pgp or and aes tool using these preshared words. or later some long passphrase