Comment by timmyc123

iCloud Keychain is required on macOS to create passkeys in Apple Passwords (which uses iCloud Keychain to securely sync them). Apple Passwords is the default credential manager in macOS (similar to Google Password Manager on most Android devices). If you want to save to another credential manager (app) on your Mac, you need to install it and enable it. If you don't have another credential manager on your Mac, that is why you can't save a passkey on your Mac and are given the option to save to another device.