This is the best time to be an independent artist. The internet and technology has opened doors that were usually reserved for those with training, credentials and connections.
Sites like
Tiny Showcase provide a platform for artist to present and sell pieces.
eBay is a huge channel for independent artist too. I know a couple of folks actually making a living there.
The downside to this is that when anybody can produce, a ton of nonsense gets out there too. It cab take a while for the good stuff to boil up to the top and get a buzz going. But if it's good, it's good!
To your other point, I haven't seen anything focusing on Black art/artists, but the few sites I have found will occasionally have a piece or two.