Answers
There is no password on your account, which means there is no password to reuse from that site that got breached in 2019. You sign in with an email link, or - better - with a passkey: Face ID, Touch ID, Windows Hello, or your password manager.
Settings → Account → Add a passkey. Your device does its little scan, and from then on sign-in is one tap, no email round trip. The email link stays as your backup - passkeys are added convenience, not a trap door.
Lost the device? Sign in with the email link and delete the old passkey from Settings. Two clicks, crisis over.