We had originally planned to go all-in on passkeys for ONCE/Campfire, and we built the early authentication system entirely around that. It was not a simple setup! Handling passkeys properly is surprisingly complicated on the backend, but we got it done. Unfortunately, the user experience kinda sucked, so we ended up ripping it all out...
His whole premise is undermined by him not doing any research on the topic before deciding to write a blog post. Proton passkeys for instance, are cross platform, and the ability to transfer passkeys between devices is one of the features being worked on by the other providers.
Proton passkeys are stored in a password manager, which he specifically calls out.
If you have a password managed and know how to use it, you’re already a lot less susceptible to the problem that passkeys are trying to solve.
Personally, I think passkeys are great for tech-savvy users, but I wouldn’t dream of recommending them to non tech-savvy people. Password managers are still used by the minority, that needs to be fixed before passkeys are useful.