Can I convert an NTFS volume to case-insensitive? If I can do it by formatting / erasing, that is fine. I have a backup. BTW, I cannot use FAT, exFAT, EXT3, EXT4 or others. I have to use NTFS.
NTFS is case sensitive (see here) depending on the namespace that it is running under. In a Win32 environment, it will be case insensitive, in other POSIX environments, it will be case sensitive. In essence, it is much more about the OS than the FS (filesystem).
Generally speaking though, this just means that the OS has the option of treating something as case insensitive (it could do case insensitive compare on its own).
There is no change that you are going to change the filesystem in this way to make it case insensitive. It would:
If you are looking for something more specific (say, convert all file names to lower case on the drive) there might be something that can be done, but the filesystem itself will remain unchanged.