Its going to affect bitcoin
While this page deals with primarily, Bitcoin, every blockchain that uses elliptic curve cryptography (ECC) is vulnerable.
Main points of vulnerability
Public/Private Key Cryptography
A powerful quantum computer can reverse Bitcoin public keys into private keys from their public keys using Shor's algorithm. 36% of all BTC are on addresses with exposed public keys. This is why it's very important to not reuse addresses and use wallets that automatically changes your address for you.
Even with this precaution in mind, 100% of addresses can be hacked during transactions by deriving the private key from the public key which is broadcast to the network.
It's unlikely that quantum computers present and issue for Bitcoin's Proof-of-Work system. Even with optimistic estimates, a quantum computer with fast gate speeds, a low error rate, and 4,400,000 qubits you would be looking at 13.8 GH/s. Not only is this much slower than ASIC's (at ~14 TH/s) which are currently on the market, but it wouldn't be economical.
Assuming it would make economical sense, quantum computers are likely to be competing with other quantum computers on the network due to the issue of them having no significant advantage.