I needed a simple text-based export of geometry from Blender (2.90) into THREE, so I wrote a Python script that exports polygon indices, vertex coordinates and (optionally) per-mesh UVs into a text file.
I also wrote a JavaScript function that parses the file into a THREE-compatible geometry.
It allows to create index or non-index THREE geometry with varying level of smooth shading:
and have per-mesh (if exported from Blender) or per polygon (face) UVs:
Here is a fiddle usage example (HTML panel contains the Python script at the bottom):
