This is a paid asset, but now you can download MicroSplat – Low Poly Look Free.
Detail this asset from Unity Store: Original Link
MicroSplat – Low Poly Look v3.5
The Low Poly Look module for MicroSplat adds several new features to achieve a Low Poly look with your terrains.
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– Hard Edge Normals makes your terrain look flat shaded
– Flat Texture mode uses your textures as a palette of colors, assigning a single color from the palette to each triangle or quad
– Wireframe rendering allows for traditional wireframe rendering, in world or screen space, along with the ability to adjust the saturation or brightness of the terrain under the wireframe rather than rendering a color wireframe.
Documentation available online
Requires the MicroSplat framework to be installed.