One of Tolkien's letters describes orcs as“squat, broad, flat-nosed, sallow-skinned, with wide mouths and slant eyes: in fact degraded and repulsive versions of the (to Europeans) least lovely Mongol-types.”
And I was thinking about, 1.) Look at the legs on these Mongolian wrestlers all decked out for a major national wrestling festival, and also 2.) how Tolkien's racist description wasn't enough, and orcs have been depicted as more and more grotesque over time. Canonically orcs more or less just look like humans, but that's not "other" enough so they keep getting turned in to more and more bizarre looking monsters.
Either way, this is what i'm thinking about when i'm laid up with the 'rona. If y'all like wrestling or buff men in tiny pants check out Mongolian wrestling. From what I understand it's a hugely popular sport there and has been for like a thousand years.
It's canon for elves -> orcs, it was mentioned in SIlmarillion i think. No idea about ents -> trolls but it's plausible because Tolkien noted Morgoth lost power to create anything so for making trolls he had to make them from something already existing. About dwarfs -> goblins it's definitely non canon, goblins are just smaller and nimbler orcs who hate light even more, because they lived few thousands years in caves (remember that it is more than enough time in Middle-Earth for otherwise hundred thousand+ years evolution taking place).