>>96152293
Orcs can't really come from anything other than elves, as they're capable of breeding with men. Meaning that they too are children of Illuvatar, unlike say dwarves whom were children of Aule given life by the one.
However, given the malice and evil spirits of Utumno, they really can't be counted as elves anymore and likely not since they had truly become orcs in the depths of time.
However maybe it's for the best there's no actual concrete answer for the origin of the orcs, and it can be a forgotten horror of Udun man was never meant to understand.