Microsoft Surface Ergonomic Keyboard not recognized as a proper keyboard
macOS Sierra does not fully recognize the Microsoft Surface Ergonomic Keyboard as a keyboard, but a workaround exists.


Install Karabiner Elements. It lets you intercept and remap keyboard input.
Launch Karabiner Elements and go to the Devices tab and uncheck everything but "Ergonomic Keyboard" so that Karabiner does not swap keys with any other keyboards attached to your computer. 
Switch to the "Simple Modifications Keys" tab. Click the "add item" button. Remap "left_command" to "left_option" and "left_option" to "left_command". Then do the same for "right" command/option keys.