“Bandaid” (for translation purpose: something that bypasses the issue ignoring other issues). It’ll work just not perfectly or as you want/need it to. (Substrate Select & Substrate shading models/slab + Landscape Layer Sample)
So the issue seems to be Landscape layer blend weights not being 0-1, not the blends itself. Also landscape layer painting no longer subtracting/overwriting (weights) when you paint over layers so you need to manually paint a layer & remove the underneath layers. Its not a quick or accurate thing to do.
Epic really needs to address this, I’m sure they have a solution or upcoming fix we are all not aware of. Because Substrate & landscapes was a subject raised back in UE5.4?
Also In case Epic also isn’t aware, how could they not be though on this, You cannot break out a slab to material attributes in anyway shape or form, So it raises some questions about RVT’s future if this is the way forward.
But for now If anyone wants a Recommendation: use UE5.6 for landscape & transfer that to 5.7.