The old Australian online tax filing system, through to the early 2010s, was an extremely 90s-looking Delphi application, Windows only for most of that time until they released an OS X port towards the end. Linux support consisted of a note on the website saying "some users have reported success with Wine". I don't believe they ever did floppy disk output though.

It's been replaced by something far nicer and web based! Though the old application was still definitely better than doing taxes by hand or having to pay for some third-party thing.