The main character's alleged sexual improprieties are a major theme of the film, but are not discussed in graphic detail.
Lydia Tár is seen naked for a couple of seconds in one scene, while washing herself from a distance. Her bare buttocks and side boob (including nipple) are seen, but full frontal nudity is blink and you will miss it.
Some kissing and scenes of seduction. There is a lesbian kiss.
Tár helps a woman put her ill mother into a chair who is nude, which is shown somewhat briefly. Not sexual whatsoever.