It depends on the product.
Vaults
To create a client-controlled vault, you will need two hardware wallets. At this time, Unchained supports hardware wallets from Trezor, Ledger, and Coldcard. For most users, we recommend using two hardware wallets so that you always retain majority control of your wealth.
To use our multi-institution custody model with the vaults product, you must have at least one hardware wallet.
Loans
Loans can be taken with either one hardware wallet or without a hardware wallet.
We do not have plans to support paper wallets or other methods of controlling private keys outside of hardware wallets at this time.
Can I use an Unchained Capital vault without a hardware wallet?
We require clients to have at least one hardware wallet to use multisignature vaults. Owning a hardware wallet ensures that your xpub (extended public key), which is used to create bitcoin addresses for your vault, will always be controlled by the private keys on the hardware device. These devices ensure that your bitcoin cannot be lost or destroyed as easily (as compared to paper or other wallets), and they can be used to recover a wallet using a seed phrase.