They make Ethernet adapters for streaming stick devices.

Here is the one we use.

• amazon.com/dp/B07N2ZHFY9/?coliid=I3OTXUDPJXAANF&colid=DCKELH4Q08N2&psc=1&ref_=lv_ov_lig_dp_it

Amazon sells one specifically for the Firesticks, BUT, it limited to 100Mb Ethernet, while the one above is can hit 400Mb+ (assuming gigabit connection).

If you get this one you could get up to 480 Mbps, but that's the most you would be able to get because USB 2.0 is limited to 480 Mbps.

The Amazon ethernet adapter works fine but is limited to 100Mbps. 100Mbps is good enough for most people. Alternatively you can get this adapter which is popular among FireStick users and doesn't require an OTG cable

https://www.amazon.com/Cable-Matters-Streaming-Including-Chromecast/dp/B07N2ZHFY9

It has a gigabit ethernet chip but you will be capped at 480Mbps because of FireSticks USB2 interface. Real world performance will be more like 350-400Mbps.