Hmm. Let me get back to you on that when I get home. It may actually not allow dynamic lighting unless you’re using a shader pack that supports it so you may need to look for a simple shader that does dynamic lighting but none of the other fancy performance-sucking features. I thought I remember the “internal shaders” activated from shader settings having an option for dynamic lights. However that might have just been an optifine thing, not iris.

Do note that iris is graphical only. Any dynamic lighting it creates does not change block light states. Lamb dynamic lights, from what I see, is a legitimate lighting engine change that updates block states with your player movement. Dunno if that matters to you or not.