Re: How to verify SegWit signature with Brainwallet ?

Actually, there's a shortcut to this!

Just get your original message,
Then remove the address from the message (copy this):

Code:

-----BEGIN BITCOIN SIGNED MESSAGE-----
I'm Lulucrypto on Bitcointalk. And normally, I'm Luluwebmaster. I sign this message at 9 Aug 2019.
-----BEGIN SIGNATURE-----
IAIAMSyjMV62EttLm3HltwmQK0HEchc80OfXKJGPEo1pIvq/st/kgWvLmREfByk3/TSbdrWLmfzoExivGSxzTOo=
-----END BITCOIN SIGNED MESSAGE-----

And paste to https://brainwalletx.github.io/#verify
It'll automatically recognize the legacy address used for that signed message.

Because either way, the message was verified using the address: 1NtMnD5BQrRvVeHDk4HXaGvXiVkUuTjhXf, not bc1q7qgn8zw75n26hd60a8ay42482mukdjrdv3cyp7.
But both can be derived from the same prv key, so there wont be a serious problem with future verification.
The only difference is: those extra steps are some kind of proof that the result legacy address was based from your SegWit address.