You cannot change it, you must setup ScreenTime and disable Siri WebSearch
May or may not be anonymized but if you click on Google stuff, its likely fair game. Not happy about this, I dont care about their default deals but they have no right to not allow your Siri searches to also respect your preference in search engine you’ve consciously decided on
Once again, very sneaky
Why are you surprised that Apple won’t let you change any default settings?