Some people are working on private, e2ee DMs and group chats for nostr. I would generally say that beyond a certain size, a group chat has to be assumed to be compromised, so using it with encryption is almost not desired as it gives a false sense of privacy.

Nostr being a successful DM protocol was not on my BINGO card but it might be necessary in the light of Telegram, WhatsApp and maybe Signal all being compromised and not private with the meta data to begin with. 

 nostr:note13hk6h6c9zrpndsvy08tr0xlvz45jfj2twfl3tp03jt08sv6kcxmqx34nax

note1x9jxtqje8fd0ut8wgtauchnr9ja7zh6kyq3tly6c3ntqrwzcselq6pdcvnn