What does a setting need to be "supported"

[Remathilis]

And to answer your question:
A "world" map is important. And by world, I mean the scope in which the setting in encompassed. Whether it is a planet, galaxy, continent, country, town, house, large dragon bones, etc.
Races in my opinion are pseudo important, only because it will differentiate said setting from other settings by the type of beings that inhabit said setting.
Classes equally as important as race choice.
Equipment, is important, how else would the players do things without a hammer? A sword? Spell components? Food? Water?
Starting Region is important because the journey has to begin somewhere, and this is largely dependent on setting size.
Monsters are important, the PCs need something to fight. Even if the monsters are other humans!
A Starting Adventure is a good idea, because it gives the players an idea of what the setting is like.
I find Variant Rules important, because this also helps establish your setting as its own creation. Obviously, most of the core would be D&D 5e related, but enough Variant Rule fluff to also give the game its own identity.

What do I find unimportant, mainly because it depends on the setting size, scope, and type are -
Religion
Nations
Culture
Calendar
Magic
Organizations

I hope you found some good insight on what I said.

Without tipping my hand too much, I will say there is a very different opinion on if a setting is designed top-down vs bottom-up. Both types of settings require different requirements. The stuff you mentioned as essential is important to a bottom-up setting, whereas the stuff you mentioned as unimportant are key for top-down.

 

[hawkeyefan]

With the ease of getting past edition books, I feel like most of the items on the list are available. Not to mention the amount you can find on the internet.

So I suppose that would leave the elements that require mechanics; unique races, new or different classes, some setting specific monsters and equipment and spells, and any alternate rules.

The rest of the items on the list already exist.

 

[Jester David]

A comprehensive fan wiki.

 

[Remathilis]

A comprehensive fan wiki.

While I certainly see the benefit of such a thing, that isn't exactly useful for some new setting not coming from a past edition or another media outlet.

 

[Jester David]

While I certainly see the benefit of such a thing, that isn't exactly useful for some new setting not coming from a past edition or another media outlet.

Why not?

Isn’t it just as useful as a big book, theoretically having the same amount of content. Only it enables bouncing between topics and reading in the order you like. Curious about a new, unfamiliar noun? Click a link.
All it needs is a starting page with a table of contents.

 

[Satyrn]

Adventures. Not just a starting adventure.

It's the only thing I think a setting needs. Everything else is just gravy.

 

[Prakriti]

A comprehensive fan wiki.

Until you mentioned that, I never realized just how instrumental the FR wiki is to my own games. It has been super-useful, not just for the articles, but for the bibliographies too. The references for any given article are pretty much a comprehensive list of all the relevant source-books for that particular subject.

 

[Tallifer]

As a dungeon master, I can fluff anything I want to recreate a setting. I do not need anything at all for older settings, because fluff is fluff, and crunch can be improvised on the fly. As for a completely new setting, nothing proposed catches my interest. (Oz would be fantastic, but there is already a far superior rpg for that: Adventures in Oz)

As a player, I might need the races, classes and possibly special spells and equipment in a published book in order to persuade the more restrictive dungeon masters to allow me to play a character from said setting. Certainly as a player, that is all I need.

 

[Jester David]

Okay, I think in the days of 2nd Edition you needed a boxed set. In 3e you needed a big hardcover.
Now... hard to say.
I think you can get by with PDFs or even print on demand books. Or, as I said, a good wiki. A lot of worlds see support via Epic Words or Obsidian Portal.

For official worlds, I think “support” is being allowed on the DMsGuild. An official PDF with a crunch update is nice as well. But I think the FR wiki is probably a better resource than any possible Realms book. https://forgottenrealms.fandom.com/wiki/Main_Page
(The only reason people want a new book is to update the world and it’s nations to reflect the changes of the last century.)

 

[Quartz]

If you're thinking about a setting as a saleable product the big one I've not seen mentioned so far is an outline history or timeline. It doesn't need to be comprehensive but rather just a bare bones.