My simple tileset working fine in CesiumJS and Cesium for Unity flickers weirdly in Cesium for Unreal (UE 5.2.1 with Cesium for Unreal 5.2.0). The tiles are sometimes completely invisible and sometimes behaving like they are semi-transparent or something. The regular CesiumWorldTerrain works fine. See this video: cesium_unreal.zip (1.8 MB)
You need to look in the Cesium for Unreal plugin, not in your project. The post I linked explains how to make the Content Browser show plugin content (enable “Show Plugin Content”), and where to look for the material instance within the Cesium for Unreal plugin (Materials/Instances/MI_CesiumThreeOverlaysAndClipping).
Show Plugin Content is enabled in the screenshot above, should the plugin itself be present in the root of the hierarchy to the left then? Or is there another more general Content Browser somewhere? Sorry for being an UE noob, but sometimes things seem unnecessarily complicated. No fault of yours of course.