I haven't made one in ages, but I have heard Calibre might be able to process CHM and possibly even generate it (cannot confirm).

The only working bookmark I have now that standalone MSDN is basically defunct (RIP, legend) is:

https://learn.microsoft.com/en-us/previous-versions/windows/...

(might wanna archive before MS redirects it to welcome.microsoft.com or something)

Not sure if that helps but it's all I got!