We did certify a LoRa module only with the RF part, so we can have the flexibility to select the STM based on the application and run our device firmware on it along with the LoRaWAN stack.
We now use it in 5 devices and when certifying the devices, the RED directive is already covered by the module’s test reports, therefore the lab is only testing it for LVD and EMC, which is very easy for battery powered devices.
I am the CEO of MClimate. My CTO did the certification and said there have been more challenging certifications for him - e.g. a device controlling a water heater with 32A relay and e-meter.
I’d advise you to get in touch with certification laboratory and ask them more about the actual tests.