nostr:nprofile1qyxhwumn8ghj7mn0wvhxcmmvqyw8wumn8ghj7mn0wd68ytfsxyh8jcttd95x7mnwv5hxxmmdqqszpxr0hql8whvk6xyv5hya7yxwd4snur4hu4mg5rctz2ehekkzrvcsuxfmc is the only desktop client that can read secure DMs I discovered today.
It can't, however write them, I still have to use Amethyst to post gift wrapped DMs.
i.e. All DMs are encrypted, but their meta data isn't, meaning that anybody can see who your DM'ing, but not what you're saying.
Secure DMs encrypt all the data, including the sender and recipient.