I just revisited the sites ranked by @theblackboard to start this conversation and found that 1/2 of the discussion forums mention are dead:
The Black Board Community Forum (www.theblack-board.com) The domain name redirects to another website. A search on the community name yields no results. So I assume this discussion forum is no longer active.
Black Visions (www.blackvisions.org/) The link from the homepage to the community is broken. After finding an alternative path to the discussion forum, I see that the most recent post is from August of 2018.
Cocoa Lounge (www.cocoalounge.org/) The URL to this website is no longer active and is currently redirected to an unrelated website.
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SomaliSpot.com (www.somalispot.com) This forum is still active and quite good. I just updated my profile and replied to a post. It looks quite good it is obviously Somali-centric, but like AALBC.com is does not matter where you are from. Just don't try any silly Somali pirate jokes.
Destee (www.destee.com) Destee is still active and judging the site quickly. It's designation as the #1 discussion forum is deserved. I updated my account on this website and introduced myself.
The Blackboard's list did not include Lipstick Alley (which I keep hearing is not Black owned) or Nubian Planet who no longer appears to operate a discussion forum.
Well the status of Black owned discussion forums, despite a couple of bright spots continues to get worse and is looking rather grim. The corporate run alternatives, as I always say, will never ever serve us.
I'll keep AALBC.com's discussion forum going as long as there are people who read it and folks who contribute to it.