There are some account-recovery mechanisms that aren't a total disaster(reset emails, no some hideously long 'really, you'll need to print this one' recovery password, potentially) but as you say they tend to be idiosyncratic and highly variable in quality. Yubico tells The Verge that services have to individually add support for Lightning connector on the 5Ci into their apps.

And you can't just plug the Lightning side of the 5Ci into an iPhone and expect it to work with any service that supports the FIDO authentication protocol - our passwordless future isn't here just yet. Notably, the 5Ci doesn't work with the newest iPad Pros at all, despite having a USB-C connector that fits. And when using the Brave browser for iOS, the YubiKey 5Ci can be used as an easier way to log into Twitter, GitHub, 1Password's web app, and a couple other services. At launch, it'll support these well-known password managers and single sign-on tools: 1Password, Bitwarden, Dashlane, Idaptive, LastPass, and Okta. The Verge reports: That means you may not have to remember your password for your bank ever again - just plug the YubiKey into your iPhone, use it to log into the 1Password app, and get that bank password. Yubico is releasing the $70 YubiKey 5Ci, the first security key that can plug into your iPhone's Lightning port or a USB-C port, and it's compatible with popular password vaults LastPass and 1Password out of the box.

Yubikey lightning adapter