When adding additional metadata parse to libraw we need to support most major camera vendors (C,F,L,N,O,P,P,S,S). Unfortunately vendor specific metadata (makernotes) is not documented and may change in format from camera to camera (even from one firmware version to another).
So we support only metadata that is absolutely necessary for common photographic processing.
For your needs you may also use call to external exiftool program and parse output (command line like exiftool -cameratemperature -csv _81E0220.CR2 ). It is easy to implement and exiftool license is free to do that.
When adding additional metadata parse to libraw we need to support most major camera vendors (C,F,L,N,O,P,P,S,S). Unfortunately vendor specific metadata (makernotes) is not documented and may change in format from camera to camera (even from one firmware version to another).
So we support only metadata that is absolutely necessary for common photographic processing.
For your needs you may also use call to external exiftool program and parse output (command line like exiftool -cameratemperature -csv _81E0220.CR2 ). It is easy to implement and exiftool license is free to do that.