I don't get what it's all about this passwordless. I make my browser (Firefox) generate strong password and store them in its password manager, this is synchronized with end to end encryption to all my devices, I have only to remember a master password. It's kind of the same but it works with every website. It is not complicated, doesn't require certificates that you may loose, and that sort of things.
Try explaining a password manager to your nana, and having her use it. Then explain to her how she can install it on her phone and have it synchronised across all her devices. Password managers are awesome, but way too technical to become mainstream. You shouldn't have to install 3rd party software for something so fundamental. The password system really needs an overhaul and hopefully this will go along way towards…
Eg., I was telling a middle aged person (50 years) about password managers and were unable to grasp the idea of it. 'Why would you store passwords in cloud based password manager from a company I have never heard of, just type a password and write it down on your diary (OS notes app) or just store it in chrome. I trust google (chrome) to keep my passwords safe rather than with some sketchy company I have never heard of (the sketchy company if one of the most reputable cloud based password management company).