Geometry Nodes - How to randomise rotation around just one axis When using geometry nodes to distribute points across an object, and then instance those points with another object (i.e. the Point Distribute and Point Instance nodes specifically), how can you rotate the instanced object around just one axis?
To put it another way - each instanced object appears (to me) to inherit its initial rotation from the normal of the source object over which the points are scattered (so instanced objects are always pointing Z up from the surface of the source object). I want to keep the X and Y rotation that the instanced object inherits, and just randomise the Z rotation.
This is the first thing I tried. This randomises the Z rotation, but sets X and Y to 0. I want to retain the current values of X and Y, and just randomise Z, but I don't see how to do that:

Then I thought I was very clever coming up with this. The problem here is that the output of the Random Float node always seems to be the same number, so the Z rotation is always the same for every particle instance. I want a random Z value for each instance:

Is there a way to actually do what I want at the moment?
Using Attribute Randomize you are able to create a new attribute, instead rewriting the existing one. Then use attribute math to add a random vector to the existing rotation.
Another useful node is point rotate, it has the ability to rotate instances in local and global coordinates: