it takes time for a new board to be included in Arduino and subsequently into PlatformIO. So when M5Paper came out the easiest way to create an M5Paper PlatformIO project, was to take a similar board, in this case M5Stack Fire, which was already available. (The key here is that both M5Stack Fire and M5Paper use PSRAM.) And later on, I guess, M5Stack engineers simply forgot to fix that.

Thanks
Felix

After a few false starts, it builds and installs on the device, so that's all good.

Is there anything I can/should do to set the board correctly? Does it matter?

for this project M5Stack engineers decided to use Visual Studio Code and PlatformIO as programming environment (instead of Arduino). Try searching with Google for Arduino esp32 platformio for more information.

Thanks
Felix

A naive question - how can I compile that back on to the device? The only mechanism I've got working to talk to it is Arduino - I see a reference to Arduino in the .ini file, but can't open it as a project in the Arduino IDE.

Is there something different I need to open it in Arduino? Or do I need to use some different method altogether.

Thanks again for all your assistance.

this is the firmware which was initially loaded on the M5Paper.

Thanks
Felix