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
replies(3):
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.