Somehow, using the new GPU Lightmass in 4.26, I got much worse results than with Luoshuang’s solution in 4.25… In the 4.26 lighting is not that bad overall, but I got very bad and visible light seams and light leaks. I’m testing with the same geometry and the same hdri… I’m a bit confused and frankly, disappointed.
I can accept a little noise but seams & leaks are disqualifying factors.