The script "update-rtlsdr.sh" can be used to update the librtlsdr0 driver used by generic rtl-sdr dongles, including newer RTL-SDR Blog V4 hardware which may not be supported by the driver installed from your default package repository.
Building the driver using this script has proven to be somewhat hit-or-miss, so I suggest you try running the default version first, and if it works, keep using it. Don't say I didn't warn you if things go wrong and you end up with no driver installed!
If you are really sure you want to proceed, run this command: ./update-rtlsdr.sh