Pay-to-Merkle-Root (P2MR).

Would add a new output type, P2MR, that works like Taproot without its key-only way to spend, to resist some quantum attacks.

A future quantum computer might work out a private key from a public key left on the blockchain for a long time. Taproot coins are exposed this way; P2MR coins, with addresses starting bc1z, remove that weak spot. It does not protect a payment waiting to confirm; that may need new quantum-safe signatures.