1.) Getting the YubiKey setup with 1Password is confusing, even for a tech-head like myself. In my situation this is YubiKey 5C NFC.
2) The YubiKey does not work with 1Password. I can enable 2FA on my 1Password account using the YubiKey 5C NFC and I can use it to unlock my account when using 1Password on a computer. However, I cannot unlock 1Password on my phone using the YubiKey because 1Password has not written the necessary code to allow 1Password to use the YubiKey 5's NFC feature.
3) Yubico advertise that the YubiKey 5 series works seamlessly with password managers such as 1Password, but this could not be further from the truth. Enabling 2FA on my 1Password account using a YubiKey requires that I also use the Yubico Authenticator app. Rather than simply inserting my YubiKey into the computer and logging in, I am required to first insert the YubiKey, then open the Yubico Authenticator app, find the login I need a code for, copy that code to my clipboard, navigate over to 1Password, paste the code, and only then can I finally unlock the application. This is not a seamless process.
In order to improve the 2FA authentication process, 1Password needs to dramatically improve the quality of their setup documentation and support website. Yubico also needs to provide a much more honest description of the process involved in using the YubiKey 5 series for password managers such as 1Password.