Forget esports setups.

Stable Porsche 992 GT3 R Setup for Silverstone - Assetto Corsa Competizione.

Note: Negative toe might still work in the qualifying environment. But all my setups will for now utilize positive or only slightly negative toe as I expect it to be the more sustainable solution.

The Porsche just feels great with a balanced race setup. Ever so slightly willing to rotate on entry, stable in the middle off throttle and again willing to just mildly rotate on exit (apart from high speed, where its pushing a bit). It might be best simulation ACC has to offer. Everything feels really round and smooth, no excessive behavior in any situation.

Overall the new Porsche needs less steering as before and it's easy to turn too much. The high steer ratio helps to be precise.
Be careful on turn in. The tires likely need half a turn or more to build temperature on the surface and they are more snappy on entry when still cold. You can get them warm more equally by reducing camber and going for more positive toe. This will cost lap time in general, but might gain you time if the car is unrealiable on corner entries for you. While the car remains the crazy rotation off throttle, the center of that rotation seems far more in the center of the car now, than around the tip of the nose, which makes it rotate more like a mid engine car. The rear doesn't feel quite as exposed on corner entry, and you get actually turn into the direction you want to go, instead of controlling a permanent slide. In Q the weight balance is still very far to the rear, hard to do anything about it. I tamed it as much as I could and again no negative toe needed here for (most of the) lap time.

Silverstone
Silverstone is a grippy track and most of the corners are downforce dependent corners apart from the few hairpins that are purely mechanical for the car. Braking in Q is trickier than in race trim, due to the missing weight on the front. You might actually experience shorter braking distances in race trim. In Q the brake bias is further to the rear to stop the front from locking up. The behavior changes quite a bit from Q to Race here. And you can still go higher with brake bias. 
Especially in the race it feels very balanced and despite the wear difference, it remained stable as far as I got into the stint. The race set definitely starts on the understeery side, but it will certainly become more oversteery as the weight balance changes and the rear tires outwear the fronts.
Silverstone is special with its swings in high speed situations. Just straighten up for the short braking periods in the esses and let it roll a while and only make tiny speed andjustments into the corners with brake and throttle. In Q the car is slightly pitch sensitive, while in race its less so.

Driving

• Aim for late apexes and dont shy away from a short shift or staying in the higher gear option in the first place
• your brake is more than a means of deceleration, it also controls pitch and especially in Q this will be key to managing rotation on corner entry - most pronounced in T2-4, but also the slow corners
• on throttle the car will keep rotating, dont just floor it as that might exaggerate it - take a close look at my throttle traces, especially at the exit of the chicane. Position is key here. Use TC3 if needed, but 2 provides faster laps and if you feel like it, switch to TC1 on exits
• dont steer too much, progress into it, be ready to steer neutral on exits.

Adjustments

• If too oversteery: Stiffer front spring, stiffer front roll bar, less rake. One click at a time.
• The brake bias is tricky. If it's too far forward the front will suddenly regain grip and the rear snaps. If too far back the rears might lock. Higher ABS here if you cannot handle it, but likely at a time loss. Clean trailing will pay off.
• higher preload can give more turn in stability, but will come with more nervous exits
• lowering front and adding rear camber might further stabilize the car (in race)
• lowering the caster also gives more predictability
• Some drivers might like a car with less rake for better drivability. It does not seem to be too problematic to lower the wing in turn for 2-3mm lower rear ride height.

Tire pressures
Aim for 27.0 entering the fast corners for solid support from the tire without surprises. You can play with the fronts at lower pressures, so they develop some temperature. Yet we have a lot of high load corners here and a stiff tire feels much more communicative than a soft one.

Lap times
Q fuel: 13L (This is safe to use for the sprint races adding the necessary fuel of 48L - maybe add 1 click of rear ride height)
R: 100L