Hello @derhaase
interesting question - which got me curious if this is actually doable on M5Paper or not.
Using all three ports (A, B and C) available on M5Paper gives you 6 GPIOs of which you can use port A for I2C (SDA and SCL) and port B and C for SPI (SCK, MOSI, MISO and CS).
I did a quick test with the M5Stack Ethernet module (which uses SPI as well) and I got it working alongside the display. The trick is to properly initialize the SPI peripherals. ESP32 has four of them, two are used internally and one is used for the M5Paper display. This leaves one to connect another SPI slave device.
Please note: I do not have the camera module, so I cannot test if it works with that camera as well.
Good luck!
Thanks
Felix