Does Diablo16 display modules support RS485?

No. Diablo16 display modules do not directly support RS485.
However, you can use MOTG-RS485 to connect a Diablo16 display via RS485. This will require one of the COM ports and a GPIO pin.
When using a gen4-uLCD Diablo16 display. It is advisable to use a gen4-MOTG accessory board. This allows easy connectivity with the MOTG-RS232 through Diablo16's configurable COM port.