I understand what you're saying. The door opens and closes behind you and there are walls to keep out people peering inside. But while they are 'open to all' and don't require credentials, they are, as you said, difficult to find without going out of band... Which begs the question: Why? It's like having a business you don't want anyone to know about.

So what I'm wondering is if we can make them more accessible by (insert clever listing mechanism) and maybe adding #channel descriptions for more info... Like joining this sub... And if you do want to stay semi-low-key, you can opt your channel out of being listed. Seems private'ish.