What was the nature of Ham’s sin (Gen 9:22)?

Was it really sinful or wrong to catch a sight of one’s father naked at all, let alone when drunk? First, note that Lev 18:7 makes it unlawful to “uncover” the “nakedness of thy father,” although, to be fair, the text does not say Ham did this, but only that Ham caught sight of Noah’s uncovered body. Still, one view has it that this is a euphemism for incest. But this interpretation is not, strictly speaking, required by the text. Perhaps merely being able to see his uncovered father was the shameful thing. This seems unlikely to us today, because for us, since family members of the same sex regularly accidentally see each other’s nakedness, the boys merely seeing their father’s naked body was probably not unusual or shameful. But Ross claims, “To the ancients…even seeing one’s father naked was a breach of family ethic.” If so, then some euphemism is meant. It is also entirely possible that Ham’s sin is not sexual but rather the fact that he has dishonored his father by mocking him to his brothers.