External keyboard doesn't show as separate keyboard to configure MBP 14,1 (13" 2017 two TB ports)

At work I have a Dell USB-C dock that my external keyboard connects to - display is connected differently. There, like everywhere else I've seen this, when I connect an external (normal PC) keyboard it asks me to identify it ("press the key next to shift") and after that I can configure the external keyboard separately from the internal one (I like to switch alt+cmd on the PC layout).

I have a new LG screen (27UK850-W) at home that connects to the MBP via USB-C. It charges the device and transports display on that connection. The screen also has two USB-A ports - they work (I connect a mouse and my default external keyboard), but the keyboard doesn't show up as a "separate" device - if I remap the keys (alt+cmd in my case) this is also done for the built-in keyboard.

Any ideas how I can work around this?
If you are looking for Modifier remap, in keyboard.prefPane exists a modifier button where you can edit it for external keyboard.
For more advanced ways, you should checkout keyboard Maestro for Macro keys and this answer to figure out what you want to do.