I suppose that switching to Brave will be one of the best solutions after all.
They have already comment this in June:
https://brave.com/blog/brave-shields-manifest-v3
I'd argue its far more trustworthy than modern day Firefox/Mozilla, they're not exactly the second coming these days.
What makes Firefox more trustworthy?
Yeah it's true that Mozilla's mostly financed from Google's anti-antitrust payments, but at least they actually made something of their own and have a trustworthy track record three decades long as a non-profit and Netscape before that.
That right there sours your whole argument. Your entire reasoning here is based on "they're probably doing something dodgy", ignoring the bit about it being opensource, or that Firefox and Chrome are at the very minimum on equal terms of "dodgyness", as you'll no doubt already know.
Tell me I can turn off the evil intent, and not just one of its manifestations, and we're in business. But you can't tell me that.
Once you've done that you're back to the same old question - why is <other browser> any better/safe/trustworth than Brave, which is arguably the only one that's gone out of their way to make sure its sustainable and not reliant on farming user data to the highest broker.
I'm sure no user data is shared with Brave's search partners (and don't pretend they don't get paid by Google and others for all the users who abandon the not-great Brave Search for a more capable service.) Google just pays them whatever they pinky swear to Google was their traffic, no reporting at all, no search telemetry, none of that. Right?
And I'm sure zero user data makes it to big advertisers who pay for full new tab takeovers. I mean, why wouldn't big advertisers throw tens of thousands of dollars a day on ads with no proof of reach or return.
Oh, it's anonymized, you say? So, just like all the other browsers?
Also, a quarter of a billion VC dollars have to be paid back at some point. You can't claim anything is truly sustainable when VCs still own a quarter of its value and it's taken VC money 7 of the last 10 years.