There is no other solution than a manual time consuming labor. The way I do it works perfectly for my workflow, fits the art style as nothing else and saves a lot of time in asset creation. Also, if other engines don’t have this issue then I’d rather use them than scrap the idea only because it doesn’t fit into the limitations of Unreal Engine. There is nothing extraordinary in having full precision normals, I’m just amused that game industry constantly makes such ugly sacrifices in its pursuit of some questionable goal.
This post I made for the awareness, I don’t expect that something will be done about it, after all Unreal Engine is notorious for its quirks as I learned it in a hard way and observed in various posts on this forum.