There's really only Firefox and WebKit derivatives (everything else you listed), for the most part. I'm increasingly of the opinion that duopolies don't result

There's really only Firefox and WebKit derivatives (everything else you listed), for the most part. I'm increasingly of the opinion that duopolies don't result in good progress, so I fully support new entrants in this space, even if I think it's unlikely they'll get near the popularity needed to compete at a high level.