Currently I'm using macports. I'm wondering if there are any graphical X11 browsers like Chromium, or Firefox, or the like that compile under X11 (and not native OSX). I want a browser that I can manage with an X11 Desktop Environment (like i3).
Chromium would be great.
I see some threads where people have asked similar questions but most of these are at least 4 years old.
I'm not sure your reason for wanting a browser under X11, but your needs might be met by running Chromium or Firefox in a Docker container over VNC. Then, you can use any window manager you want.
For example, here's my container that exposes Firefox through OpenBox.
Firefox over VNC on Docker Hub