I would actually fundamentally question why chat is treated as “visible only if you actively go looking” in the first place. Categories and Topics are not treated this way and I kind of feel like neither should chat be! Chat should be, as I’ve just said elsewhere, “a first-class citizen” in Discourse. That means it should, IMO, be visible by default in top-level views (e.g. category list, etc.).
Now certainly this has to be considered in the context of whether “chat on topic” actually ends up existing in the initial implementation or not. Last I heard they were considering dropping it as a launch feature, which I think may be a good idea as the UI/UX considerations are challenging, and chat is by its nature most often less laser-focused in topic. A category is a good balance of focused-enough, but not too focused to define a chat.
If chat on topic does get included, then obviously making all chat channels visible (but not joined) by default makes less sense, but at the least I think category-level chats should still be just… visible… all the dang time. Maybe you can actively hide them, or switch between “my channels” and “all channels” view (with “all channels view” on by default) with the pencil or something.
Think about how Discord works in this context for what is likely to be the most familiar metaphor for many coming into Discourse chat. Obviously Slack is another one, but it is default-private, whereas as Discord, and many Discourse instances, are more of a “default public”. So again that informs my preference here. Curious if others agree though (and sorry if I’ve semi-hijacked your topic Jim!).