Sauron is an aggressively industrializing, totalitarian leader who brooks no dissent from his horde of entirely disposable & interchangeable minions, and whose goal is to conquer all Middle-earth so that he might subordinate its peoples to his 'better' vision where (his) order and rationality (as he defines it) reign supreme. The Free Peoples meanwhile are a coalition whose members seek to maintain their independent kingdoms and traditions (in fact Aragorn's entire character arc centers around the restoration of the kingship over the Dunedain).

This is utterly ass-backwards, while Tolkien personally disdained allegory (especially when done this hamhandedly), if one must be drawn at all then it's pretty damn obvious that Sauron is a left-wing tyrant. The emphasis on industrialism and totalitarianism might be more akin to 19th-20th century leftism, but the core drive of centralism goes all the way back to the French Revolution, with the revolutionary regime starting the French Republics' various efforts to annihilate the regional autonomy & languages of regions like Brittany & Occitania. (Meanwhile the arch-traditionalist and integralist right, as exemplified by the likes of Action Francaise, supported the regions and in AF's case was led by a proud Occitan, Charles Maurras.)