Whoa, Nelly! Never thought I’d be posting this, but here is how to make FRx to run with GP 2015.
From Jan Harrigan: How to use FRx with GP 2015 – FRxBuzz
Yeah, it makes me shudder too.
How to use FRx with GP 2015 – FRxBuzz
Reporting & BITips & Hidden FeaturesGP 2015
Archived post from 2016. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.