There's no setting for that, Google is intentionally not giving you that choice. You can append &udm=14 to the search URL in browser settings, but that constraints search results to the "web" subcategory, so you also lose fairly useful features, such as the calculator, weather infoboxes, etc.
> Note: Turning off “AI Overviews and more” in Search Labs will not disable all AI Overviews in Search. AI Overviews are part of Google Search like other features, such as knowledge panels, and can’t be turned off