What interesting marketplaces where you can sell your product do you know of?

It seems to me that offering your product on a marketplace resolves many issues that you would otherwise face and also makes you target a well-defined niche.

There are many platforms that offer an app store with apps that integrate with the platform. However, most of them don't allow you to sell your product directly.

The only such marketplace that I can think of right now is Github marketplace - https://github.com/marketplace . What other such marketplaces do you know of?