@ahasty @ati1 @linmob You should be able to use #Thunderbird for #PGP encrypted email (with mobile-config-thunderbird), or webmail instance that supports it like #SnappyMail or any other webmail using #Mailvelope extension in Firefox.
Not sure about #YubiKey, #NitroKey or alternatives as I've never used any, but they should connect to the Librem's USB-C port. The #Librem5 has a slot for a PGP smart card ( #LibremKey ?) to store private keys so you could also use that. Hopefully, someone who's used that can see your question and answer, or you can ask in Purism forums or pmOS Matrix room.



