When the language is marked as Klingon (tlh), recognize track as such.
tlh comes from tlhingon-Hol, aka Klingon.
Yes, Klingon is an actual language, and I have tracks of it in my library.
Heh…According to Adding Local Subtitles to Your Media | Plex Support PMS follows ISO 639-2
So either the article is wrong, or it’s a bug 
good point. I did check and concur.
The original subtitle I was using was an embedded subtitle tagged with tlh. Ive never had an issue with tagged lunges not being recognized before.
I read the support article you quoted and see it refers to external subtitles. I followed the instructions adding an external Klingon subtitle in the way described. It also not recognized, but it displays differently.
I have attached a screenshot to show the way they are displaying on my system. The last 2 tracks are Klingon.
