Regarding the use of Megascans with Unreal Engine, it seems the guys at Quixel are not fond of open source projects using and redistributing their assets: https://help.quixel.com/hc/en-us/community/posts/360008583998-Megascan-textures-in-open-source-Unreal-projects-
Would it be acceptable to submit the project source without the Megascans assets themselves but a list of their ids so other UE users can download them on their own then?