Hello @kokany
short answer: not easily / not together with the display.
Long answer: the issue I see is that the SPI pins used for the display are not accessible from the outside. This means it would need a second SPI instance using the pins available on port A and B. Unfortunately the M5-Ethernet library uses the first SPI instance hard-coded. See here.
So yes, M5Dial can be extended with Ethernet, but not together with the display or one would need to modify the M5-Ethernet library accordingly.
Please note: it's entirely possible there is another way I do not see right now.
Thanks
Felix