Ooofff. OK, in an effort to help improve matters, I'll give a blow-by-blow of what I'm seeing on latest build.
Practice session only; Sebring 12 hr; 7:00pm start time. LMP2 class selected so I'm getting the Oreca and Ligier, and I'm driving the Ligier. Scripted weather, which starts off first 25% of 2 hr session with partially cloudy and 73 deg, but then changes to clear and 75-77 deg, which of course because it's setting sun should be going the opposite way (i.e. colder).
I do now notice the graphics options are different. It's selected the "Auto" GPU once again (grrr... previously had my 2070 selected) and the new MSAA 8X antialiasing setting (these have changed from previous "levels" I think). Fullscreen, desktop resolution.
Display settings are all car/track settings to High, shadows to Ultra, X16 aniso, particles to High. Frame rates about 128 fps, which I think is a tad lower than I was getting.
On leaving pits, for the first few laps the lighting is changing wildly from bright to quite dark. Headlights make almost no difference. It seems I have high clouds that are occluding the sun, but the experience is very disconcerting. Clouds look OK, can't tell if significantly different to before. Next thing I notice is that with headlights on, from cockpit view, in Ligier, there are no under-car shadows at all from cars in front (which I think has been reported before with Ligier). This extreme lighting variation continues until the clouds dissipate enough that there is less sun occlusion. Going into Sunset Bend, the scene is almost entirely washed out and bright as you exit the corner onto the front straight, in a quite severe change at early-to-mid corner. No other corners experience this.
After about 15 minutes driving I exit cockpit to look at replays. The replays don't show such extreme change in sun lighting the scenes. All cars now have undercar shadows. I let the session runabout 5 more minutes without the sun completely setting; I have the expected God rays in some camera positions as the scene overall darkens about as you might expect.
I'd also note a bit of a difference between the two car models. Either the Ligier is more reflective, or there seems to be a difference in the light quality on the two car types. I'd also say there is considerably more bloom on the headlights of the Oreca than the Ligier, the latter has very crisp non-bloomed front headlights with distinct lenses, the Oreca is a blur of white. Is there some difference in the car models themselves I've previously not noticed, or did it somehow load in lower-quality models for the non-driven cars?