We are looking at FROST and other techniques like MPC.

There are new event kinds and it does leave some metadata around. However, we encourage use of private relays and will offer private-relay-as-a-service to business/groups that require extra privacy. All of the PSBTs and proposal notes are encrypted but there is still metadata.

We could have used a custom backend instead of Nostr but wanted to make it easy to self-host. Implementing something like FROST or MPC will require more backend/coordinator components to operate.