I was convinced that Apple Basic Ads on iOS didn’t give search terms / search data and I had to run big boy Apple Advanced Ads on the App Store to get the search terms.
Check out https://app-ads.apple.com/cm/app/advancedreports/create, it turns out you can find keywords for Apple Basic Ads, it’s just tucked away.
What I saw was a monstrocity of the basic ad targeting: basically any keyword that would target a download was not relevant at all to my ad.
My next step is to run Advanced search result targeting in the App Store on the keywords which I think are most likely to convert