Though the IMEI is on the modem part, using probe-rs on the app MCU will not be able to access it on it’s own. Maybe a trick as for the modem firmware update does it, where an app is loaded to the RAM of the app MCU, which then provides access to the modem. But I don’t see, that this is worth the “efforts” to be developed. Beside the IMEI, there is also an ICCID, IMSI (and in some cases the EID) and in my experience it’s just common to read them and print them on the UART with some “pre-production image” or using a “production stage” in the zephyr settings to control, if that is written to the UART or not.
