You can change the camera model metadata with ExifTool using the -Model= option. Example:

exiftool -Model="Kodak Hawkeye Instamatic" image.nef

That writes a new value to the Model tag in image.nef. Replace the quoted text with whatever camera model you want to set.

A few practical notes:

• Run the command in a terminal or command prompt from the folder containing the file, or use the full file path.
• ExifTool typically keeps a backup of the original file when it writes changes.
• This only changes metadata. It does not actually convert the RAW data to another format, so compatibility is not guaranteed.

If Lightroom still won’t open the file, a more reliable approach is usually to convert the RAW files to a supported format such as DNG or update Lightroom to a version that supports that camera.