Signing in to Chrome OS

Since Chromebooks use Google accounts for logging in, it should be possible to involve a YubiKey by following the guidance in this Google article.

 Warning: It's possible for your Chromebook to become a trusted device (in the "eyes" of your Google account), in which case, two-step verification (using a YubiKey) won't be required for every login.

If you want to perform two-step verification every time you log in to your Chromebook, follow the steps below.

 Tip: This will not apply when you "lock" your Chromebook.

1. On your Chromebook, once logged in, click on the clock, which can be found at the bottom right
2. Click the gear icon to open Settings
3. On the left, select Security and Privacy
4. Towards the middle of the window, select Manage other people
5. Toggle off Show usernames and photos on the sign-in screen

Now, any time you log in, you will need to enter your username, password, and perform two-step verification. To undo this, follow the process again, but toggle back on Show usernames and photos on the sign-in screen.

Accessing web services (after signing in)

FIDO2/passkey and FIDO U2F, two of the most often used functions of the YubiKey, should work on Chromebooks to sign in to services via a web browser. Yubico Authenticator may work on your Chromebook, but from Yubico testing, it is not 100% consistent, so your mileage may vary. See this post for additional information on how to try it out. Note that, although the linked comment mentions that it works, extensive testing has shown that not all devices/configurations work.