How can I set it upwhat exactly is not clear about the documentation (https://pve.proxmox.com/pve-docs/pve-admin-guide.html#_two_factor_authentication) ?
If you can give me the steps It would really help cuz I'm not that experienced with these stuff.you add the keys to the users, and enable TFA for the realm (it's probably a good idea to use a test realm first to verify everything is working, otherwise you might lock yourself out).. if you want to use yubico's OTP variant, check their docs for how to setup the authentication server.