My guess is you’re near a location that has an AppClip (super small and fast app) and Siri thinks that this AppClip is useful to you. The idea here is that if you actually went to this museum/attraction you would want to buy a ticket, so Siri gives you this small app to do so (you don’t need to download the full app from the App Store, just press “open”).
To clarify, this is not an ad, but an unlucky Siri Suggestion and it does not invade your privacy.
From the Apple Developer website :
When your App Clip is associated with a specific location, you can register your App Clip to appear on a place card in Maps so people can open it from there. It can also appear as a Siri suggestion and in Spotlight Search as needed.