Earlier quoted context omitted.
Brave is unethical. The key problem is they insert themselves into the revenue stream without the consent of the web publishers. It's fine to block ads entirely, but substituting your own ads and collecting money from that is wrong.
I'm not sure I see the clear cut ethical dilemma you do. Option 1. block all ads, publishers receive no revenue. Option 2. block all ads, user opts in to unrelated ads, user can choose to give some of the proceeds of seeing those ads to publishers they utilize. How can (2) possibly be worse than (1)?
Option 0. block no ads, publishers receive all of the applicable revenue from their preferred network
It isn't clear to me from the website what happens if the publisher is unaware or unable or unwilling to claim revenue generated through this fringe browser's alternative revenue mechanism. Who ends up with that money? Is advertising even shown? Is the user aware of whether or not the publisher is in a position to claim revenues of the ads they're seeing?
Depending on the answers to those questions, the addition of (2) could be worse for these publishers if it makes some users who otherwise would've (begrudgingly or otherwise) chosen option (0) feel morally justified in switching over to (2), converting their real (0)-derived revenues into unrealised (2)-derived theoretical revenues.