I’ll check those links in more detail when I have a chance, but off the bat, the normal map tutorial in the info listed on the youtube page is one I’ve seen and it’s showing the “purple” style output that in my experience does not give usable results in MSFS. This link:
Conveniently the preview image on that link shows the “purple” output that looks very broken when applied in MSFS. And that page links to 9 year old Gimp plugins for a very old version of GIMP.