As pointed out, these do exist. I've been using several over the decades. And chrome forks too.

They all tend to lag behind over time, until the fork is eventually too old and it's either abandoned, useful changes I was relying on are dropped, or becomes just too old compared to upstream to be fully compatible (and thus just annoying to use).

Just the burden to upkeep the upstream changes, in either firefox or chrome forks, seems to be significant enough that I'm quite pessimistic on the lifespan of these projects.

You might just as well do your own thing, and don't pretend to be a mainstream browser replacement altogether.

Keeping up with an already built browser is too hard so we’ll create an entirely new browser that takes even more work?

The way I see it is "I'll have fun at something that feels interesting"

Yes and those forks exists and are a solution now.

But long term, I would much rather see a truly independent open source browser engine.

> which might possibly influence what features they implement, their stance on various web standards etc.

Unless you’ve got some examples to back this up, it’s FUD. Posting hypotheticals is how rumours start, and this is just stirring the pot.

Conflict of interests is a real thing to worry about. I wouldn't trust scientist working in tobacco company on cigarette harm, even if I have no evidence of wrongdoing.

FYI https://librewolf.net/