Non-asset file packaging issue

Following this page to get a path for the Content directory, I was able to load a text file (Content/Text/Preamble.txt) while in the editor.

FString Path = FPaths::ConvertRelativePathToFull(FPaths::GameContentDir());
Path += TEXT("/Text/Preamble.txt");
FFileHelper::LoadFileToString(Preamble, *Path);

However, when I package the game, the file isn’t found. In Project Settings, I’m including the directory as an Additional Non-Asset Directory to Package, and I also tried Additional Non-Asset Directory to Copy, but neither worked. Is there more that I have to do for it to be packaged? Or does that path just not work on packaging?