Ok, so how to get MIKKTSPACE to work correctly with sketchfab?
Here is test case if needed
@stkopp the best way to get your model working as expected is to export tangents in the data you upload (typically this means using a "rich" format like FBX).
At the moment, when the tangents are not exported, we do compute them but not using mikkt approach and it leads to artifacts.
At it seems that mikkt is becoming a standard, we'll probably update to this soon but in the meantime you have to export the data.
I have found that this is a problem in blender exporting tool. I did export of same model via substance painter and problem gone.
Glad to know you found a workaround!
And indeed, I think we do not support tangents exported from blender yet. @waleguene could you confirm this?