Same question here.
In Photoshop I can use the Proof Colors -> Monitor RGB setting and everything will look exactly like it should do.
Without this option in either Photoshop or Affinity Photo my images look slightly too bright, looking like the gamma is too low.
My displays are calibrated to 2.2 gamma, 120nits, 6500K using displaycal. The profile is assigned to the screen via DisplayCal Profile Loader. Using Windows 10.
Every program - but Photoshop (Proof Colors workaround fixes it) or Affinity Photo - is working correctly like Davinci Resolve Studio, Premiere, Fusion, AE, Gimp, Windows Photo Viewer, Edge, Video players (Rec709 to sRGB conversion) etc.
In Affinity Photo I can assign the monitor profile to the document itself, but each new layer on top suffers from the same issue again. As a possible workaround, is it possible to assign the ICC profile to each layer?