I put in for a return on the not quite right Thunderbolt 3 hub and the seller wasn’t prepared to pay the return postage. The item cost $32.94, they offered a $15.44 partial refund & said keep the device.
So I ordered another similar device for $46 including delivery- this one behaves properly.
Meanwhile Amazon has refunded the full $32.94.
So I’m actually a few dollars ahead & have two T/bolt 3 hubs.
The first one is going into the Mac User Group multi-device A/V connector bag for use by any guest presenter with a suitable MacBook Pro.