I decided not to wait until the problem might be fixed. Therefore, I downloaded Zinertek Enh. Airport Graphics from the MS Store. I am quite happy with it, it makes the runways visible again even in snow. Not perfect (regarding the snow problem), might have something to do with layers and tire tracks, but the runways are visible again, which was very difficult especially with small airfields in winter. I also like the result better than with the very simple enhancement for ground textures from flightsim.to.