sorry, my mistake then. i just skimmed through the garuda purana, and it turns out that "adultery" have never been directly explained in the chapters.. as far as i know, idk why. there are spouse-related issues explained there, but it's not a direct answer to adultery acts.

however, i've heard that issues with adultery have been talked about in other puranas, e.g. bhagavata purana. here is an excerpt in the bhagavat purana explaining adultery and etc:

A man or woman who indulges in sexual intercourse with an unworthy member of the opposite sex is punished after death by the assistants of Yamarāja in the hell known as Taptasūrmi. There such men and women are beaten with whips. The man is forced to embrace a red-hot iron form of a woman, and the woman is forced to embrace a similar form of a man. Such is the punishment for illicit sex.

(Bhagavata Purana, Canto 5, Chapter 26, Verse 20)