Lightmapping artifacts

Hey all - could someone help me understand why my lightmaps produce some nasty artifacts? Here some examples. You can see that my geometry is clean and has good normals and shading.

I should mention I am letting Unity generate the lightmap UVs.



6737995--776233--upload_2021-1-18_11-27-21.png

Please read the following pinned post: [FAQ] Blocky artifacts appear when I bake a scene. How can I fix them?