The biggest flaw of DeltaChat, is IMO the fact that you cannot easily use PGP keys generated in Thunderbird. But it is still a great app.
#DeltaChat - messaging software that works with e-mail
https://www.linuxlinks.com/delta-chat-messaging-software-email/
Discussion
You can. I did, although I generated them with GnuPG.
In #DeltaChat, go to settings > advanced > manage keys > import secret keys.