Question: How do you sell cargo?

Yeah, I know that seems basic and should be easy to figure out, but I have not been able to successfully sell cargo I've bought or earned through salvage since 3.24 launched. I've tried every landing zone and every combination of in the ship, out of the ship, on the elevator, and in the warehouse that I can think of. I've "sold" cargo from the ship's inventory and been told to manually deliver it only for nothing to happen when I manually deliver the cargo. I've sold cargo and selected the auto-unload only for the cargo to vanish and I don't get paid. I've put the cargo in the warehouse only for it not to show up at TDDs. I've watched videos and guides and done what they show, only for nothing to work. That leads me to think it's got to be user error. At first, I thought it was bugs but if others are able to sell cargo most of the time, I must be doing something wrong.

So, the question:

Could someone post a detailed workflow they use when selling cargo? One they've reliably used again and again to sell purchased cargo, RMC, and the like?

As an aside, I've done tons of the new hauling missions and enjoy them! Those seem to work fine these days and make adequate-ish money, but I'd really like to be able to take the vulture out and actually be able to sell the RMC I collect.