Information on wake-up pins.
The 8 pins that can be used for wake-up from EM4:DeepSleep seem to be PC0(ESCAPE), PC5(SCL), PC7(RX), PA5(MOSI), and back side PB1, PB3, PD2, PD5(IMU_PW).
Reference Manual, 24.3.12.3 Pin Function Tables, Table 24.3. GPIO Alternate Function Table
PC0 is also defined as ESCAPE to avoid bricking. It is not impossible to use it as ESCAPE function when it is LOW for a long time and as a wake-up function for a short time.