There's an issue with subsurface scattering on the Quixel Megascans Foliage Material which renders foliage too darkly when facing the sun. Thanks to user pcvrnzcmdrnemysis007 on the Unreal Slackers Discord, here is a quick fix so that all your future grass assets are properly rendered on your landscapes.
00:00 - Intro
01:15 - Nanite Fix
06:17 - Extra Step for Non-Nanite Foliage