ScriptReference/RectTransformUtility.ScreenPointToLocalPointInRectangle

[docscomments[bot]]

ScriptReference/RectTransformUtility.ScreenPointToLocalPointInRectangle

https://docs.unity3d.com/ScriptReference/RectTransformUtility.ScreenPointToLocalPointInRectangle.html

[radiatoryang]

Really important: Note the "cam = null" usage note in the docs!
Also: this function won't actually give you the coordinates in anchored / UI pivot space... to convert:
localPoint += rect.rect.max;
(see here for info)