@cr3al no experience with flashing via phone, in general I had no issues with bruce/nemo etc, and M5StickC devices, just be sure its correct firmware for StickC StickC+ StickC+2
the battery connector powers everything, including RTC. But, yes, when the external battery is fully drained RTC time is lost as there is no built-in battery for the RTC.
@konstantint Thankyou for doing that! very useful.
I see your config puts the reset pin definitions directly in the correct driver sections for the touchscreen and LCD so that those driver handle them correctly. I think this is better than doing it separately the way I suggested :-)