Google says you can't turn off AI overviews in the main search engine. I'm still seeing the "Labs" icon in the top right, with some checkboxes for AI features, but those checkboxes are no longer respected—some queries will bring up an AI overview no matter what. What you can do is go find a new "Web" filter, which can live alongside the usual filters like "Videos," "Images," "Maps," and "Shopping." That's right, a "Web" filter for what used to be a web search engine. Google says the Web filter can appear in the main tab bar depending on the query (when would a web filter not be appropriate?), but I've only ever seen it buried deep in the "More" section.
Once you do find the Web filter, the results will look like old-school Google. You get 10 blue links, and that's it, with everything else (Google Maps, answer info boxes, etc) disabled. Sadly, unlike old-school Google, these are still the current Google web results, so they'll be dominated by SEO sites rather than page quality.

Google says AI Overviews are rolling out to "hundreds of millions of users" this week, with "over a billion people" seeing the feature by the end of the year, as Google expands AI Overview to more countries. //

The power-user way to use Google Search web now takes a lot of clicks. You'd want to click on "more" and then "Web" for actual web results, and then to get Google to actually pay attention to the words you type in, you'd want to click "Tools" and change "all results" to "verbatim." Alternatively, you could also find a more web-focused search engine instead of Google.