More details, please.

Are you wanting notes that are stored on relays encrypted so only you can see them, like a relay-hosted version of Obsidian or Joplin?

Or are you wanting encrypted direct messaging, like Signal or SimpleX?

We have encrypted direct messaging in 0xChat and Keychat, and many flagship clients, too. It's a mess right now, because they aren't using the same DM spec, though. You'll receive some messages in one app, but not others. 0xChat seems to be the best about showing all of them.

We don't yet have the relay-hosted version of Obsidian or Joplin with encrypted notes only you can read.