Clouds follow the simple formula of z=x, passing through the origin at x=0, z=0. I've traveled and teleported quite far to see if they spawn anywhere else in the world and can say with reasonable confidence that they don't. I'm using Mantle 1.10.2-1.1.5, Natura 1.10.2-4.1.0.80, and Forge 12.18.3.2185 with no other mods installed. Same thing happened in Natura 1.10.2-4.1.0.73 as well.
Picture:

Is there any progress about it ?

Also applies to the clouds in the End.

https://i.imgur.com/bh17SEg.png Clouds have been fixed!

Also see #398