I had same problem on my return to game after long break. My first impression was that game died when i was away. But no, it's alive and kicking
What did change is that MA added chat channels with global range. So there is no longer a need to gather in one place like old PA to trade your shit. You can now do your thing whatever it is and spam planet specific trade channel. Only when somebody PMs you, you setup a place to meet. So the answer you are looking is: there is no trade hubs anymore. On caly twin peaks seems to still be alive if you have small quantities you would like to sell to resellers - other than that ppl trade remotely via global trade channels.