I think this is a misunderstanding of something that occurred roughly 12 years ago. It was not really “behind users backs” it was an announced ‘feature’ (and in the release notes) of the Unity desktop environment (“Lenses”), and a part of a larger pivot towards integrating web features into the OS (I believe progressive web app integration and the ability to connect to online accounts like Nextcloud, Google, etc, were rolled out and promoted in the same release).
It did cross a line (mixing local and non-local search queries) that many users considered inappropriate, but remember this was a time when privacy concerns were not nearly as widely held or discussed as they are now (pre-Snowden era), and while this controversy did certainly exist at the time, it has become inflated with time to something larger than it was.
It was a bad decision, or maybe it would be more accurate to say poorly implemented and not well thought through. But a decision where I think they legitimately did not anticipate it to be as controversial as it ended up being. In subsequent releases the contreversial aspects of the integration were, acknowledged, fixed, and in some cases eliminated.
There was no disingenous deliberate data collection or anything like that, and queries were proxied. But many people (myself included) just felt local searches should stay local by default, and there were some flaws in the implementation where some info good potentially leak.
It was a decision that should never have happened in my eyes, at least not in the way it did, but it is very far the malicious conspiracy many people make it out to be. It was rolled back when it became clear many users were unhappy with it, and the intent was not to mislead user or collect data. There have been no other big privacy controversies in the 12 years since that time afaik.