Andy,
Interesting you mentioned HDR. Right next to the Affinity listing on Apple App is Aurora. I feel sure you must have looked at it. It is so simply to use as a stand alone and you two would fit like butter and bread. We all know that HDR requires multiple shots of one subject at different exposure settings. Should use a tripod, etc. The right shot just happens, tripod or not. One of the reasons to shoot in RAW is the ability to change elemental settings such as exposure, +1,-2,-1,-2 and save as such. This takes a bit of trial and error in Affinity but it works. One shot at a time. Export one at a time.
But what if, shoot in RAW, get your image, process in Develop to fix as best as possible, go on to Persona and finalize. Then go to Export and choose HRD which would change necessary exposure settings for HDR. Then export to your Aurora plug-in with three or five shots ready to process. No tripod needed! One good RAW shot altered as required to process in HDR!
Just a dream.