Couldn't find a better place to post this, so I thought I might post here again.
I downloaded the digital Wii U eShop version of NSMBWii to replace my defunct physical copy. As I have an American Wii U and the digital version was never released in America, I grabbed the European version instead. With custom firmware, it works perfectly. But the issues I'm having right now relate to my save data. I was...pretty far on my American save and I didn't want to start over, so I downloaded SaveGame Manager GX on Homebrew to my standard Wii to extract it, after which I did a bit of hex editing to swap the region to Europe.
However, no matter how hard I try, I can't install the save back into my Wii U. The reason for that? It seems that SaveGame Manager GX, contrary to what many websites say, is incompatible with vWii, and I can't find any vWii builds of it, nor can I find any alternate programs that work with vWii. When I try to run the app, it just gives me some "facelib database is missing" error. I do not know what on earth that means and Google was no help. I even tried a download on some random German site that claimed to be vWii compatible, only to get the same download error. There seemingly was a vWii build at one point, but the official link on SourceForge is broken. I never had any of these errors when using the app on my actual Wii.
So I have three options: (a) find some way to get SaveGame Manager GX working on vWii, (b) somehow trick my actual Wii into thinking that I played the European version as opposed to the American one, so I can install my save data to that and transfer it from there, or (c) find a way to turn my extracted gamesave into the official data.bin format. I'm not sure how to do any of that.