Not an expert, what are your project and post process settings? for lument and reflections.
Getting the feature back is not going to be easy, you better stay on 5.3.
I also have been told that he could be some settings to tweak, you could look at
- disabling the screen traces (in the lumen reflection settings of the post process)
- enable hardware raytracing for lumen in the PRoject settings with Ray Lighting Mode at “Hit-Lighting for reflections”
- making sure raytracing is enabled to r.raytracing.enable 1