There's a website I use irregularly (I sign in maybe every other month) that doesn't use passwords, doesn't use sign in with X, etc. Instead, they have a form to enter an email address, and they send you a magic link to log in. Since it's a generic email field with no password prompt, my password manager doesn't offer to fill it in for me, and my browser helpfully offers every email address I've ever put into a form. I now have 7 accounts with this website; half of them were created to get a new API key, the other half were to submit feedback that I'll never get notified of responses to because I can't be signed into multiple accounts at once and they don't email me about comments.

I expect that by sometime next year I'll hit 10 accounts with them.