Thanks, @jlampel, the first and third comment by Troy are really helpful, the second one is rather technical and cryptic to me. The big question is always whether Blender treats my texture in a way that doesn’t corrupt it for its later use. So, as Troy said, a “Normal Map” should be treated as “Data” and not be transformed in any way. I would therefore set the setting for the “Output Device” in the “Color Management” to “None”, save the file with “Save as Render” unchecked so that no “View Transformations” are executed and would then load the file as “Non Color Data” .
