I have tested the latest 5.6.1 release regarding the bug where Nanite-enabled trees, painted with the Foliage Tool, do not cast any shadows, direct or indirect, when Evaluate World Position Offset is enabled in the material. This happens even with Lumen turned off.
Full details here: Unreal Engine 5.6 – Nanite Trees Painted with Foliage Tool Don't Cast Shadows When WPO Is Enabled
Is this issue currently being worked on, and can we expect a fix soon?