Most major SaaS apps support it, the major hardware provider I see recommended is yubikey although Google makes one as well. See also U2f. It's super easy to implement, try it out for yourself in Flask.

https://www.yubico.com/solutions/fido-u2f/

https://cloud.google.com/titan-security-key/

https://github.com/herrjemand/flask-fido-u2f

Indeed. I spent 10 or 15 minutes trying to figure out if they are selling a physical device, like a usb 'key' or are just selling 2 factor authentication with mobile phones. And I'm still none the wiser. It's pages upon pages of buzzwords and nonsense.