USB floppy controllers are very different from "real" floppy controllers. USB controllers are doing the floppy formats in firmware, so the PC it connects to can

USB floppy controllers are very different from "real" floppy controllers. USB controllers are doing the floppy formats in firmware, so the PC it connects to can only use it for formats the USB controller knows about, which is typically just your standard PC formats (one or two). Traditional controllers are way more flexible and is only limited to what kind of flux modulation they can handle (an Adaptec AHA-1522A can handle FM, for example, while the later ones can't). Then it's up to your software what you can read. I use an old PC (old enough to have a floppy drive and a good controller, but new enough to have ethernet) to read non-PC floppy disks of many different formats. But certain stuff it can't do, and that's typically Apple and Commodore. For that you need a direct flux reader like the Greaseweazle or Kryoflux or one of the others.