Using exiftool, the command would be:
exiftool -Orientation= /target/dir/or/File

Replace /target/dir/or/File with the files and/or directories you want to process.

This command creates backup files. Add -overwrite_original to suppress the creation of backup files. Add -r to recurse into subdirectories. If this command is run under Unix/Mac, reverse any double/single quotes to avoid bash interpretation.

You can use exiftool to remove the orientation tag:

exiftool -Orientation= /target/dir/or/File

Replace /target/dir/or/File with the files and/or directories you want to process. If run under Unix/Mac, use single quotes to avoid bash interpretation.

• To suppress the creation of backup files, add -overwrite_original.

• To recurse into subdirectories, add -r.