The version that maintained this legacy support? —essentially a "waterfox browser old version" of the modern web.
Waterfox 56.2.14 (2019) or Waterfox 2019.10 (the final pre-Classic branding release). waterfox browser old version
Using Waterfox Classic on the modern web became an exercise in whack-a-mole. Google Docs would lag. Discord’s web app would throw "unsupported browser" warnings. Reddit’s redesign would stutter. The version that maintained this legacy support