According to Wikipedia, Green Browser is not only discontinued but it’s based on Internet Explorer (ew!) which is to say, it’s Windows-only. You don’t want that.
falkon, as it was a candidate for the browser when we came out with the first LXQt version of Lubuntu. It was a little unstable back then, so if you’re not on 19.04, that may not be the best solution, but it’s still worth a shot.
Another possibility might be
netsurf, as it’s got really low requirements but they seem to work hard at making it generally compliant with the modern web. It’s written in pure C with its own rendering engine so it’s built for speed. They claim 16MB is all the RAM you need.
If you don’t need to have all the bells and whistles of the modern web, you might try
The fact of the matter is that the modern web is incredibly demanding these days. Try shoving in as much memory as you can.