I have updated the image with firefox; the help files can now be opened from the IDE. I realized that I may not be able to actually use codesys for my use case, so I will be putting this down until further notice.
I thought for sure I was the only person on earth who wanted to put an industrial IDE onto a video game console, but here we are! tl;dr I did get it working, instructions further down Codesys-4-linux has given me a ton of issues, partially because of the different architecture, and partially because it references old or deprecated packages. Also, newer versions of Codesys require the webview2 runtime, which, I understand, is very difficult to get working via WINE, and breaks just about every time...