I use GIMP for the textures. I’m satisfied with the output of blender using the MSFSTookkit as shown in Flying Theston’s videos - particularly this one: [026] PBR Texturing Models In Blender - Microsoft Flight Simulator 2020 SDK Tutorials - YouTube He’s using a different image tool, but the steps are the same.
And if the texture you downloaded didn’t have a normal map, I’m happy using GIMP with the following instructions from Jen Abbott (not FS related, but useful): How to make texture maps in GIMP for use in Blender | Blender 2.8/GIMP 2.10 Tutorial - YouTube
Regarding the earlier comments in this thread, all my normal texture files look the standard blue with some highlights in pink like Flying Theston’s video.