A proper instruction for RD9700 is here https://www.technouz.com/3973/how-to-use-a-generic-usb-ethernet-adapter-rd9700-on-mac-os-x/
This is the only manual I've found so far that has ALL necessary steps.
In particular step 7 is critical (install drivers from x86_64 folder).
I managed to get my noname adapter working, but the internet speed is only 5mbps although I have 100mbps connection :(
Step 1: Unplug your USB adapter.
Step 2: Restart your Mac by clicking the Apple logo in the top-left
corner and then Restart. As soon as your machine restarts, you’ll hear
the Apple chime. Hold down CMD + R immediately after hearing the chime
to boot in to Recovery Mode.
You can release CMD + R once you see the Apple logo and a progress
Step 3: From the top bar, select Utilities and then Terminal.
Step 4: In the terminal window, you need to type the follow and then
hit enter: csrutil disable. You may be prompted for your Administrator
Step 5: Now from the top bar, click the Apple Logo and then Restart.
Step 6: Your Mac should now restart back in to the normal operating
mode. It’s time to install the drivers. Click here to download the zip
file and extract it to your Desktop.
Step 7: Install the RD9700 driver located in the x86_64 folder and
then restart your Mac again.
Step 8: Once your Mac has rebooted, open Terminal and enter the
following then press the Enter key: sudo kextload
Step 9: Reboot again.
Step 10: Now plug-in your USB Ethernet Adapter with a live ethernet
cable. Open System Preferences and go to Network.
Step 11: Press the + button in the bottom right and select USB 2.0
10/100M Ethernet Adapter and then click Add.
Step 12: Disconnect from WiFi and you should notice your network
connect still works through the RD9700 Ethernet Adapter. In addition,
you will be able to share internet using the RD9700 too.