I think @Leo tried this once and he found it way too annoying.
I tried it, but, although the Yubikey is supported in Firefox, Google only supports it in Chrome and I won’t use Chrome.
My personal opinion. For work, I use a service that requires MFA. When we first started using it, a Yubikey was required. It was annoying. I had to make sure to always have it whenever I might need to sign in. Since in my case it would be an “on call” basis, it was extremely annoying to have to run around the house to go find it. As soon as they also allowed OTP via an authenticator app, I switched immediately.
Don’t get me wrong, I understand the security of needing a physical security key. But, at least for me, the convenience of OTP makes it much better for me.