Keeping in line with their amazing design, their Sign Up page asks either for Google Sign In or just your email. Their signup with email, interestingly acts as an email verifier as well as is easier on the user to start with. After you provide your email, they need you to provide a temporary password (like an OTP) which essentially verifies your email.
This is pretty neat compared to many other flows which require you to setup a safe password and then verify your email later. Notion's entire onboarding is a different story though and it seems like its never going to end. Full marks for the signup though.
The next noteworthy sign up is Product Hunt.