At the time of writing, there is a bug in the Metahuman editor in UE 5.6. If you have a language different from English in the editor during assembly, the character may turn black, and the bug may also be related to the enabled Metahuman runtime plugin. To fix the error with black textures, you need to turn off the Metahuman plugin. runtime, and switch the editor to English, then rebuild the character (the old one must be deleted.)