I'm not quite sure how to phrase this correct, but item frames are not affected by light. Other entities that were already loaded before I updated the version are not dark
BTW: Because search bar is hard to use I'm not sure if this has been reported already.
Environment
Superflat world, started in 19w37a, I reloaded it in the new snapshot and item frames were very dark. Note: I'm not like 30 million blocks out, I'm right near 0,0.
Also present on 19w38b