Confessions of a Frustrated Housewife (1976) on Netflix

Aging wife desperately wants to sexually satisfy her husband, but he's losing interest and cheats. She seeks advice even from prostitutes but nothing helps. Tired from trying, she falls for her husband's son who reciprocates.

Antonio, a rich old Italian industrialist is married in a second time to the fascinating middle-aged Laura. After 7 years of marriage, things work wearily. There is even some problem in the bedroom, he can no longer satisfy her sexually but he embarks on sparkling purely sexual relationships with very young girls. At the same time, he makes his son Claudio, who is a university student abroad, return home, and help him with his business at his small factory. He also asks him act as a companion for his increasingly lonely and disconsolate wife, while he is having fun with presumed business trips with Danish students. Son and stepmother, however, become more and more close-knit, until the crime happens, or rather, more than one. She then becomes aware of herself and leaves the house going to live with an ultra-feminist friend Diana, while Claudio returns to his studies. Her husband searches for her, begs her to come back to him. The woman, who finally feels free, refuses. Antonio, being cuckolded and horned, does not take it very well.

—cineraglio