UPDATE: I removed the drive and put it in my hardware jig for testing. It is recognized by my Windows 10 Pro desktop but it doesn't display any details; i.e, it appears in the list of drives but there is no info "NNN free of NNN" displayed. Attempts to list the volume -- dir L: -- comes back with "The parameter is incorrect."
DISKPART shows it as a drive and I can make it the selected drive and list the partitions. DISKPART detail on partition shows: Letter=L, FileSystem=RAW, Status=Healthy. Disk Management lists the drive and lists its file system as RAW.
I ran EaseUS (which is able to read RAW partitions) and I was able to recover a lot of files. Of course, now comes the difficult part where the user has to figure out which files are meaningful to them; e.g., which files were previously deleted which they no longer want, etc.