I know you mentioned having tried it but my experience with DDG has been pretty good and it’s what I use (edit to add that I’m not doubting your experience with it has been poor and this isn’t intended to sound flippant).
I see Kagi come up a lot. I don’t trust engines like Kagi not to link my payment data with my search history, personally. They’re a US company, so consider what that means in the current state of the world and privacy. I haven’t deeply investigated the validity of it, but the Kagi CEO allegedly harassed a journalist (minor edit, a blogger) who had a critical take on their service, and supposedly they were founded as - you guessed it - an AI company.
And sure, DDG is a US company, too. But they don’t really have anything personally identifying to link my searches back to me. I can accept the ads (though I have uBlock), which are only contextually targeted based on search keywords. I don’t think I’d use their browser or extensions, which would have a much more privileged place in my “tech stack”, but for search it does well enough.
Like others here, I use mine as a sort of “kiosk” for smart home stuff by using Guided Access to lock it to a single app. If you have a Mac you could also put it into real single-app mode via Apple Configurator policies, but it’s more time-consuming to set up and if the app stops working there’s no way to fix it short of restarting the entire iPad (whereas you can end Guided Access, restart the app, and start Guided Access again).