Note that this also applies to ReactOS (an open sourced OS implementing the Windwos API up to Windows XP and Windows Server 2003), on which the only supported browser is also Firefox 52 (in its ESR version which is an "end of support release" that will also expire due to lack of maintenance).
Older versions of Chromium may still work (and probably better than this Firefox ESR, as there are more developers active on it and finding workarounds for limitations in these older OSes).
ReactOS however is still being developed and could increase the support for more Windows API that would allow it to run modern versions of Chromium, LibreOffice, Javascript (including frameworks like jQuery, Node.js, React), Firefox (now in process of dying), Ruby/Rail, Python, and even could compile modern versions of Firefox (even if its developement is now slowing down and usage is dramatically decreasing, due to many unsolved problems and too many security issues in its supported plugins, suffering from an antique integration framework). ReactOs also will allow running standard Linux applications and new Windows API are also slowly being integrated, with improvements as well in the kernel.