How can HR Help Desk Agents view the Primary Contact's language preference in an SR?

Summary:

Our Canada HRHD Agents are required to respond in French to any users who indicate French is their preferred language for communication. They are currently having to manually review and re-assign individual tickets that require responses to be in French. This is very manual and time consuming so the business have asked if there is a way to make the language preference visible so tickets can be filtered and mass assigned to a French speaking agent.

We have tried using the Language Code filter available in the Service Request page but this does not show any values. Is this filter based on user language preference, and if so how can that be enabled? If not, is there another way for Agents to quickly and easily identify which SRs are from users with Canadian French language preference?