The Ultimate Fighting Championship, acquired in 2016 by Endeavor (then WME-IMG) for the hefty sum of $4B, is approaching the end of its seven-year TV deal with Fox, which expires in December. As Endeavor looks for a new package for the once-high-flying circuit, the process goes to the heart of one of the thorniest and most complex parts of the media business: sports rights. As with many other televised sports, ratings for the mixed-martial-arts circuit on the Fox…