I have been having several issues with triangulation, basically any boolean operation gets me a triangulation error on UE4 import (of an FBX generated with ROP FBX Output), unless I uncheck "Detriangulate polygons" on the boolean node, but this destroys the rest of the mesh for a procedural approach, shouldn't Houdini have some operation to detriangulate on demand? I tried to use PolyDoctor before export but it fills any hole I made with the booleans.
But what really made me open this thread is that I got a triangulation error after I UV unwrapped a model using Labs Auto UV.. I'm quite at a loss here and I don't really know what I am supposed to do to avoid getting this recurrent error, also based on my knowledge, UVs have nothing to do with how a mesh gets triangulate.
Any help is appreciated thanks.

Did you ever figure this out? I'm getting similar errors when trying to import an allembic RBD simulation into Unreal. I'm using a triangulate/divide node to triangulate.