Maybe not, but you can install 1Password later, go to the account with the iCloud passkey and use it once, then use 1Password to generate a new passkey for that

Maybe not, but you can install 1Password later, go to the account with the iCloud passkey and use it once, then use 1Password to generate a new passkey for that account. This flow is also generally better than trying to port keys between accounts, which adds a lot of security concerns.