[noggin]

The USB port on the fire stick is only USB 2.0 that is why it works faster on your laptop, you will be getting all the benefits of USB 3.0
The u green Gigabit adapter is only available in USB 3.0, this gives a little bit of a speed boost over buying a USB 2.0 adapter which is only 10/100.
Hope this makes sense.

I know this, but it all happens at the speeds where difference between usb 2.0 and 3.0 should not matter. I get 40mbps via fire TV stick, 80mbps via laptop and 120mbps via another adapter on the laptop. Looks like both otg and ugreen adapters have issues...    

https://forum.kodi.tv/showthread.php?tid...pid2796340

Running iPerf3 on my Amazon Fire TV Stick 4K with a USB OTG adaptor and an Anker USB3 GigE+USB3 Hub combo device I got 270Mbs throughput into my MacBook Pro, via a Netgear Gigabit switch (Smart Managed model) and a Thunderbolt Gigabit Ethernet adaptor.  Over 802.11ac 5GHz WiFi (into a Ubiquiti access point in another room) I achieved c. 80Mbs.

Of course once you add SMB or NFS protocol support on top of this then other things come in to play - but at the network level I get much higher throughputs over GigE than you are reporting.  How are you measuring your speed?

For info I'm using this OTG adaptor https://www.amazon.co.uk/gp/product/B00M7XQ6O2  and this USB 3 GigE+Hub combo https://www.amazon.co.uk/Anker-AK-A75140...B00PC0J1VC