I asked this question on StackOverflow, but I wasn't entirely satisfied with the answer:
GLU has been deprecated and should not be used in new code, but some legacy code requires it.
Many online references I've found refer to the gluTessellation as a preferred method for triangulating polygons. I can't find many other that mentions that these functions (or really any of GLU) have been deprecated or that an alternative should be used, including on the [GLU Wikipedia page](\https://en.wikipedia.org/wiki/OpenGL_Utility_Library). The Khronos OpenGL wiki mentions that the view/perspective glu* functions use the matrix stack that no longer exists, but nothing related to the gluTess* functions.
The posted Stack Overflow answer implies that the OpenGL functions used by gluTess* also no longer exist in current OpenGL implementations, and any software relying on them simply won't work.
For other glu* functions, GLFW has mentioned alternative libraries, like [linmath](\https://github.com/datenwolf/linmath.h). If we should not be using gluTess* functions, is there a list similar to [this one](\https://www.khronos.org/opengl/wiki/Related_toolkits_and_APIs#3D_File_Libraries) that provides third party implementation of polygon triangulation?
P. S. apologies for the ugly links (still on the 2-link, new user limit)