And what a pain it is to keep multiple keys registered on all of your services. At least one of those keys should be stored off-site, which means making trips to the off-site location to swap that key, bring it home, and get it registered also. Do that again when you want to register a new service.
Sure, not being clonable is a security feature, but it's a huge pain to keep multiple keys registered on all of your services.
For real backup resiliency, you should have at least 3 keys, one of which you keep off-site. Presumably you keep one at home and one with you. Want to sign up for a new service? I hope you're at home where you can access two of your keys to register them. Then sometime later you need to go to your off-site location to swap that key, bring it home, and get it registered also. Do that periodically so all of your services are on all 3 keys.
Unclonable hardware keys work well enough when it's for a corporate service. Lose the key? Just visit IT and have them give you a new one or overnight it. But unclonable hardware keys are a huge pain when used personally with multiple services.
TOTP secrets, while less secure, are much easier to manage. You can write them down, store them on a USB stick, or store them in an online account. You can send them in a message or even read them over the phone. Ultimately the average user is more concerned about losing access to their account than being attacked by a nation state.
Google has chosen poorly in forcing Google Prompts on all signed-in phones and tablets when 2-step verification is turned on. It nullifies the extra security of a hardware key, turning all of your phones and tablets into weaker second factors, whether you want it or not.
To disable Google Prompts and just use your YubiKey's U2F, you could enroll in Google's Advanced Protection Program. But then your TOTP and backup codes would stop working, as would any third-party apps that need access to data in your Google account.
The YubiKey, by the way, is a great hardware TOTP key, in addition to being a FIDO U2F key. TOTP has an advantage over U2F in that you can keep backup copies of the TOTP secrets. Of course TOTP is less secure because it is phishable, but U2F is a real pain because you can't make backup copies of the key.
The display in action on a Q1: https://www.1000bit.it/lista/q/q1europe/q1microlite.png
Close-up shot in a Q1: https://www.peel.dk/Q1/img/SN615-05.jpg
Brochure: https://archive.org/details/TNM_Self-Scan_II_panels_for_data...
There are videos of the display being demonstrated on YouTube. Search for Burroughs Self-Scan.