Smoothing Posterized Image in G'MIC

What algorithm exist that can solve this kind of image?




Note how it looks structured, but it is also clear that a lot of details would be better if filled while maintaining structure.

Due to the nature of the algorithm of the filter used to create this involving counting binary string, it is not possible to generate a smooth output with algorithm change alone.

I know that the best approach so far is Smooth [Patch-Based], but that doesn’t solve large patches.