Seams on my model

Sani

Why do my uv seams on my model create visible seams in substance painter even if layer has no textures. only channel values, or even if my model has no layers at all

poopipe

You've split UVs at an edge with averaged normals in a place where other normals are causing them to be bent away from perpendicular to the face.

Solution...

Fix your normals and/or move your UV seams

Neox

the normalmap has to cover for every decision you make on the lowpoly. but it can only do so much, dependent on its texel density and bit depth. and even at a lot of resolution and 16bit depth, things like these might still happen.

normalmaps are no perfect solution that can cover every single issue you could run into.

i wonder why you have placed UV seams on this area to begin with. looks to me as if you could planar map that entire side in one piece.

pior

To add to the above :

• The fact that shading seams may show in Substance Painter is 100% irrelevant, since Substance Painter is (obviously) not your target game engine, and likely not the context in which you'll capture your final renders either.
• Based on your screenshots alone it looks like your model was not triangulated before baking anyways - and that will always cause shading issues. Not triangulated = no control over the shading behavior, and no control over the casting of rays at the time of baking. Considering that + the fact that you placed these seams right in the middle of an area that shouldn't have any, it's not surprising at all to see shading issues appear there. It's actually to be expected.