Mag: I would say give it your absolute best first to research and find that out. Try going to company’s page, reviewing team members, finding the HR manager. If that does not work, try linkedin. If there are multiple people with similar HR titles, try to email or message one of them and express how much you love the company and would like to put your best foot foward and address the cover letter to the hiring manager. Ask if they would be able to help you and share the first name.
If that does not work, the worst case scenario, address it to: Dear (Name of the Company) Team. Eg: Dear Pangian Team.