You can always make a key layout file for the keyboard. Android keymaps are binded to the unique product ID and vendor ID of the remote / keyboard. You would only need to figure out the product and vendor IDs for the keyboard and determine the scancode for the enter keypress. Once figured out, change it's binding from, "ENTER", to, "DPAD_CENTER".
The easiest way to get the scancode for the, "ENTER", keypress is by using this app.
https://play.google.com/store/apps/details?id=innerlife.keyboard.multilanguagekeymapredefiner
Install the app and launch it with your keyboard plugged in. Go to settings and there should be a way to test each button press. It will give you the scancode. Test any and all button keypresses.
To figure out the product and vendor IDs of your keyboard, plug the USB dongle into a PC and follow these steps.
https://www.synology.com/en-global/...s/How_do_I_check_the_PID_VID_of_my_USB_device
Beyond those steps, KAR should be able to help you implement it, if he decides it's viable.