FIDO passkey Cross-Device Authentication (CDA)

I try to understand how I can login to eg a web site with passkeys on a device where I do not have the keys in any way. A practical use case example to explain: I have an account at LinkedIn. I have added a passkey in 1Password for LinkedIn. I go to a laptop where I do not have any passkey stored, nor 1Password installed (for example if I visit a friend). My testing is done on Linux laptop (LMDE 7). Two separate questions: 

1. On Firefox, I cannot find any option to choose Cross-Device Authentification. Is it because this function is not implemented in Firefox, or am I doing anything wrong?
2. On Chromium I can right click in the e-mail box and get a meny where I indeed can choose Cross-Device Authentification, a QR code is shown up. I then open my Android phone (/e/OS "de-googled OS"). But I cannot find any procedure inside 1Password or any other method to scan that QR code and login with the Cross-Device Authentification method stored in 1Password. Should it work? 

Reference: Passkeys FAQ at https://fidoalliance.org/passkeys/