Honestly, this causes me much uncertainty in regards to something like Google Authenticator or other TOTP solutions (not exactly what the post is about, but very adjacent when you start considering the points of failure).
I mean, Google's solution in particular has a "Transfer accounts" option that lets you use QR codes for a backup, but that still feels somewhat worse than having desktop software as well like KeePass and some password/biometrics protected database file like .kdbx that I could open on my phones, tablets, computers etc.
Apparently the closest you can get on the desktop is Authy, which is a TOTP client that runs on multiple platforms: https://authy.com/download/
There was also WinAuth, but it seemingly isn't updated anymore, at least since 2018: https://github.com/winauth/winauth
To me, software like that feels infinitely more portable and more suited for backups, versus some vendored device like YubiKey which costs close to what a new Android device might cost, making it less affordable to many.
But in regards to Google and other platforms that have their own opinions about how to handle logging in and their bespoke multi factor implementations? There's even less chance of something portable being viable.