Logging in to a personal service from your locked down corporate machine with a passkey works like this:

1. Start to login to the site.

2. When it gets to the point that you would choose to use a passkey if you were logging in at home, there should be some option that lets you say you want to use a passkey on another device. You can use that to tell it you want to use a passkey that is on your phone.

3. It gives you a QR code to scan with the phone, and then you complete the login using the passkey manager on the phone.