Possibly useful if you have old Apple ][ disks laying around:
Many years ago I graduated and lost access to Apple ][ machines at school, but still had a bunch of floppy disks for them.
Then just a few years ago I happened to stumble across a tool called disk2fdi http://www.oldskool.org/disk2fdi for MS-DOS, that can read Apple disks using IBM hardware. I was able to use the trial version of that (from MS-DOS on an old IBM compatible) to recover images of my disks.
I transferred the images to a newer Linux machine, and was able to use dos33fsprogs https://github.com/deater/dos33fsprogs to extract individual files and confirm that the recovery was successful. I also tested some of the disk images in an Apple ][ emulator.
I also have a couple of old TRS-80 disks (possibly a version of CPM?) that I have not been able to recover, although I haven't really tried very hard either.