Be aware that there were several incompatible formats around when 5 1/4 and 8 inch floppy disks were in use - see https://en.wikipedia.org/wiki/List_of_floppy_disk_formats. Incompatible as in, the wrong drive model and/or the wrong controller card will be unable to read a given floppy disk. Common example: Apple II or C64 5 1/4 inch disks, even if the physical disk used is the same, a standard 5 1/4 inch PC drive on a standard PC controller would be completely unable to read them.
This is not a problem at filesystem or file format level that can be solved in software - different drive systems encoded data on the disks in a different way.
To make things worse, there were actually incompatible media types: Soft sectored, and various hard sectored styles. Different magnetic (coercivity) grades also could sometimes give you surprises.
The first step in recovering data from such a disk will probably be to find out what system (which machine, which OS, which drive model) originally wrote that disk, then checking what hardware options are available.