Thanks a lot for the quick reply. Out of the two solutions you provided in #3415, the one adding #define __has_include(x) 1 worked and the code could compile with Arduino Due. 
I didn't have luck with using GxEPD2_display_selection_added.h though.
If you don't mind, I want to ask a followup question regarding the project in #3413. After compiling, the display doesn't show contents correctly. Sometimes, it flickers after resetting the Due; Other times, it is just dead. This was tested with the example GxEPD2_Example.
I have read a few posts here regarding Due as well as in this topic you recommended.
My wiring diagram is shown below, which I think matches the recommended wiring in GxEPD2_wiring_examples.h and the photo you posed in this topic. I would really appreciate it again if you could share some advice.
Chris
Image credit
Update 4/14/23, 6:19 PM
- Very faint images could be shown with 3.3V supply.
- Switch VCC from 3.3V to 5V at the right timing (haven't detected a pattern) could display the correct images.