I just opened and used saved-as to save it as a tcw file. ## EDIT ## forgot to mention, I then used the e-pack function in v2017to ensure the materials were located correctly so they will open on someone else's computer. ## END EDIT ##. Looking at the other thread, it looks like they were going to try and get mtl materials into 2017, but I guess they run out of time, and just implemented it in 2018 instead.
An alternative to 2018 would be to find a program that can open the ogj with mtl, and re-save as a suitable format, the file opens ok in meshlab, but the file formats I tried exporting from MeshLab didn't work with materials, I did use Carerra to open the obj, and export as 3DS, this opened ok with materials in 2017. Sketchup apparently has a 3rd party plug-in which can open obj files, and TC2017 can open sketchup files with materials, but I have not tried the Sketchup plug-in.
Maybe Murray will see this thread, as he knows more than myself about mesh objects