I've been storing TOTP codes in on my Yubikeys for many years now, it works pretty decently. They have an app for it (https://www.yubico.com/products/yubico-aut

I've been storing TOTP codes in on my Yubikeys for many years now, it works pretty decently. They have an app for it (https://www.yubico.com/products/yubico-authenticator https://www.yubico.com/products/yubico-authenticator) which has gotten better over the years. For redundancy I've stored keys on two devices.