Here you are:
https://orbxdirect.com/demos
One of the deepest sky textures:
https://flyawaysimulation.com/downloads/files/18029/fsx-hde-sky-textures-v20/
I'm voting for Pacific Northwest and HDE2 converted sky textures!
Delete "ShadersHLSL" folder from the p3d, right mouse click on "Install_Client.msi" file, then click "Repair". It's the easiest way to recover original shaders.