So, in this question, I saw that it was mentioned that all the races of Middle-earth, save the Elves, fought both for and against Sauron during the War of the Last Alliance.
The Silmarillion states:
All living things were divided in that day, and some of every kind, even of beasts and birds, were found in either host, save the Elves only. They alone were undivided and followed Gil-galad. Of the Dwarves few fought upon either side; but the kindred of Durin of Moria fought against Sauron.
Presumably, the race of Orcs would have been included within that category of "all living things". What, if anything, do we know about the Orcs who fought against Sauron? Do we know anything about what happened to them afterwards? Could they have been the ancestors of the unaffiliated goblins who appeared in The Hobbit?