In this example, we are going to sign a message for Bitcoin. 
import { useDynamicContext } from '@dynamic-labs/sdk-react-core';
import { isBitcoinWallet } from '@dynamic-labs/bitcoin';

const SignMessageButton = () => {
  const { primaryWallet } = useDynamicContext();

  const signMessage = async () => {
    if (!primaryWallet || !isBitcoinWallet(primaryWallet)) return;

    const signature = await primaryWallet.signMessage('example');

    console.log('signature', signature);
  };

  return <button onClick={signMessage}>Sign message</button>;
};
You can also sign a message with a specific address type (payment or ordinal) or protocol (ecdsa or bip322-simple) by passing extra params in the signMessage options. 
import { useDynamicContext } from '@dynamic-labs/sdk-react-core';
import { isBitcoinWallet } from '@dynamic-labs/bitcoin';

const SignMessageButton = () => {
  const { primaryWallet } = useDynamicContext();

  const signMessageWithOrdinalsAddress = async () => {
    if (!primaryWallet || !isBitcoinWallet(primaryWallet)) return;

    const signature = await primaryWallet.signMessage('example', { addressType: 'ordinals' });

    console.log('signature', signature);
  };

  const signMessageWithPaymentAddress = async () => {
    if (!primaryWallet || !isBitcoinWallet(primaryWallet)) return;

    const signature = await primaryWallet.signMessage('example', { addressType: 'payment' });

    console.log('signature', signature);
  };

  const signMessageWithEcdsaProtocol = async () => {
    if (!primaryWallet || !isBitcoinWallet(primaryWallet)) return;

    const signature = await primaryWallet.signMessage('example', { addressType: 'ordinals', protocol: 'ecdsa' });

    console.log('signature', signature);
  };

  return <>
    <button onClick={signMessageWithOrdinalsAddress}>Sign message with ordinals address</button>
    <button onClick={signMessageWithPaymentAddress}>Sign message with payment address</button>
    <button onClick={signMessageWithEcdsaProtocol}>Sign message with ecdsa protocol</button>
  </>;
};
Notes:
  • Some wallets don’t allow you to specify the address type or protocol. In this case, we’ll just default to the address type and protocol that the wallet supports.
  • If you don’t specify an address type, we’ll default to the address type that the wallet supports or ordinals address.
  • If you don’t specify a protocol, we’ll default to the protocol that the wallet supports or bip322-simple.