You could zip the files you want to protect with passwords and they would be protected on Windows and Linux. Or you could put all the files in one big zip file and password protect it. And if the files are important you could copy them to another device and keep it in a separate secure area.
The security of the files on the drive isn’t really an issue. They are protected as well as one can do these days.
I am trying to take the final step of locking the drive down. I want to ensure no one can add files or try to replace files on the drive. Essentially a software version of the “read-only” hardware switch on some flash drives.
I have come across a utility or two that claim to create a CDFS partition. But I believe most of those are hardware dependent and pretty dated, so it wouldn’t work on most modern drives. The sites also did not instill confidence of getting clean utilities.