Every website which has an authentication system has their own implementation choice mix of cryptography, encryption, password requirements, and growing ever larger, their choice in supported 2fa technologies.

Its sometimes hard to find out what a site may support, and thankfully there is a community directory site that lists many sites and their supported style of 2fa. From SMS, to email codes, to hardware keys this site attempts to document much of the different implementations and the informational pages on how to set each one up. It also includes a twitter button for tweeting at the organization to ask them to support 2fa better.

https://2fa.directory/