2FA for desktop client app

Question

Hi,

I was needing to see if there is a way to setup 2FA for desktop client app outlook?

Here is the scenario:

Most users have iMAC desktops or macbooks. Everyone has an O365 account, but the machines are not domain joined to Azure nor do we login to a local domain. All users login locally to the machine and utilize the outlook app that is installed on the computer. None of us login to the Microsoft portal to check our email it is only through the local desktop client app outlook.

What we are trying to figure out is how do we get 2FA to work each time a user opens up the outlook client on their desktop? Is this at all possible? If perhaps we had conditional access policies enabled would this work than? Are we able to setup conditional access to local client apps or is this strictly only for cloud apps?

Thank you,