By specification, the DNT header field only admits two possible values: "0"
or "1" (or no such header if the user has not expressed any preference):
https://www.w3.org/TR/tracking-dnt/#dnt-header-field
Extensions were thought up though:
https://www.w3.org/TR/tracking-dnt/#dnt-extensions
However, none has ever been defined. And none will ever be defined because
the DNT specification was retired in January 2019.
Also, normal human beings do not read HTTP headers. And machines do not
understand free text. You had better write emails to administrators of
websites with trackers.
