After some testing, found the problem to be the Sharpen and FilmGrain are set to 1 (ON) in the config settings by default now.
To go back to acceptable clouds, edit UserCfg.opt in the LocalCache directory.
Change Sharpen and FilmGrain values to 0 before starting FS & save the file.
Result of the relevant config section:
{PostProcess
Enabled 1
EyeAdaptation 1
ColorGrading 1
Sharpen 0
Fringe 1
LensDistortion 0
Dirt 0
LensFlare 0
FilmGrain 0
If you modify your graphical options in FS, the Sharpen & FilmGrain will go back to the default value 1, requiring to quit FS & changing again these values in UserCfg.opt
For non HDR monitor owners, you can also bypass the greyed HDR setting ON by setting HDR10 0 at the beginning of the config file. However, I found no difference changing that HDR setting.