Hi! I am trying to achieve normalized UV density for the cave mesh.

Firstly I used fused + remesh, to make sure I have even vertices along the mesh floor, ceil, walls all connected

But then...

UV-Flatten gives nice results with not so many seams, but UV is not normalized, different density everywhere
UV-Unwrap gives even density, but then UV is not smooth with million of seams around.

Is there really no idea solution to this, except manually making perfect UV layout in external editor?

assignators
Is there really no idea solution to this, except manually making perfect UV layout in external editor?

no, there is no solution to this, not even an external editor can flatten a tube without a seam.

I would say pick more and better seams to get uv's with less distortion. You've got to gut the cat before you skin it.

Got it, thanks!