For Shor's algorithm, you would need the public key as a starting point.

This is why addresses that use a pubkey (without any hashing) are immediately vulnerable.

Someone else in the thread also mentioned lightning nodes, which reveal their public key often.

BlueSlime

bitcoin

So what are we doing about the quantum elephant in the room?

I’m guessing some BIPs and solutions would accelerate if quantum became a threat. 

Would the threat always be from the perspective of reverse engineering an address or theoretically could it create collisions with the private key without needing to know a corresponding address?