Testing with the Nordic Distance Measurement library has achieved pleasing results while not using a Front End Module, but preliminary testing with a FEM hinted that maybe it isn't possible to obtain accurate distance measurements while using a PA/LNA.
This is mostly conjecture at this point, as there may have been a separate issue with the FEM that didn't relate to the Nordic Distance Measurement library. Nevertheless, I thought it prudent to get an official answer from Nordic about whether there's anything to keep in mind when using the Nordic Distance Measurement library in conjunction with a FEM.