I’ve bought, returned and tried a second one to try to get the PowerExpand 8-in-1 A8383 USB-C hub to work at Gig Ethernet speeds on my MacBook Pro. It’s plugged into a Gig Ethernet hub via a Cat 6 cable, and ethernet is the only thing plugged into the PowerExpand. The PowerExpand is the only thing plugged into the MBP. Other Macs on the same hub are working perfectly at 1000T, but both of the PowerExpand’s I’ve tried will only work at 100TX (as seen in System Prefs > Network > 10/100/1000 LAN > Details).
Since I’ve now tried two of these, it’s clearly not a hardware fault (as Anker tech support suggested). But what is going on? The MBP performs 10 times as fast on WiFi as it does via the A8383.