What are new/unknown/unpopular platforms to sell B2C “apps”?

This is a bad idea from a business standpoint, but a comfortable one psychologically. I know because I've done it. It's a bad idea business wise because a niche product hidden away in a small marketplace is more likely to fail than a niche product ignored in a large marketplace because the small time marketplace provides less exposure and niche products need exposure to reach niche customers.

But it's comfortable psychologically because it avoids the higher volume of rejection that comes with a higher volume marketplace. And by making things more difficult for myself (yourself) there is a better causal story when the project fails...the Windows Phone wasn't a business success and that wasn't in my (your) control is an easier failure to rationalize than failing in the Apple App store. There's no merit in making things harder than they need to be.

Microsoft Teams may be such a Future Platform.