I’ve just tested the new Lumen version in 5.6, and the High quality mode is currently not usable. Global illumination shows noticeable artifacts such as splashes or flickering when moving closer or farther from surfaces.
While it may be computationally efficient, the visual instability makes it impractical.
Foliage rendering remains highly unstable, even with fully 3D assets and Lumen Hardware enabled.
Even at Epic settings, it’s far from stable. This becomes especially apparent when trees overlap in the background, where noise and flickering become very distracting. I’m unsure whether new console commands were introduced to improve this behavior.