Yes, can be flipped. For now, you need to manually flip the screen in the M5StickC Plus code. Later on, if time allows, or if someone wants to tackle it, it will auto-flip. It is a low-hanging fruit in the code, just needs to be added to the sub-menu.
To manually flip it in the M5Stick Plus, in the Arduino code look for
static iunt8 display_flip and change the value from 1 to 3.
All are welcome to modify the code to their liking. If I can do it, anyone can do it
The ported code has many many opportunities for improvements and for simplification. Some are quite intuitive, like screen arrangement, that anyone could edit and change without knowing coding.