> Also... Is flushing your whole keys down the toilet a problem you run into often?

It's a potential catastrophe I'd like to avoid if possible, but the catastrophe is not inherent to any other key I have.

House key: Make new copy for 10 USD. Alternatively, get a locksmith to unlock the door and change the lock. Even more alternatively, break a window or door. I still get into my house.

Car key: Make a new copy for >10 USD. Alternatively, call roadside assistance and get them to tow me somewhere I can get a new key. More inconvenient, still very possible.

TOTP 2FA and passwords: Password databases can be backed up, and so can TOTP seeds. It's inconvenient to do so, but I can at least still just leave copies around everywhere I can, so that it's extremely unlikely that I'll be completely locked out.

Yubikey: Making copies is literally impossible, so I'll need to buy two or three keys from the get go, and get them all out every time I need to add a new key. This is a huge inconvenience that no casual user will ever do (they might do 3-2-1 if it was set-and-forget, but Yubikeys aren't). If I don't do this, I lose permanent access to my accounts. There is no safety valve built in to the system. If I lose my key, I'm fucked.