PC: How does one host a public campaign?

Obviously lots of people have the ability to host a campaign that is available for anyone to freely join (regardless of Friend status). I cannot figure out how. The only privacy settings available to me are FRIENDS & INVITE ONLY. How do I set up a game to allow randos to hop in?

I realize it may be open by default, but I played for a couple hours and no one joined which I found suspicious as it’s Day 1.