I would like to add my J3 as a device on my LAN in order to use a Wifi router that is also on the LAN (in my home) with several Linux/Windows desktops and laptops already connected. Is this a valid scenario for usage of your device?
Unfortunately we don’t have any information regarding whether the Samsung Galaxy J3 would be compatible with the USB2-OTGE100 network adapter.
Support for ASIX-based network adapters is on a per-device basis, and it is entirely up to each manufacturer whether or not support is available as Google does not require this functionality on handsets. It may work, but it might not. We have no way of knowing.
You might be able to contact Samsung and get additional information as to whether the adapter is supported or not.
I am sorry I don’t have a more definitive answer, but I hope this information helps.