r820tweak is a modified RTL-SDR driver that exposes the R820T2 device gain stages and filters and makes them accessible through a GUI app.
You just need to launch your SDR program (e.g gqrx) like this:
r820tweak gqrx and it will automatically preload the modified driver
Then you need to run
which will launch the GUI app that manages RTLSDR settings
Because it takes eons to get the new features in the gnuradio source and then the software that uses it.
libusb-dev and a gcc compiler are neeeded to build the project, e.g:
sudo apt-get install gcc libusb-dev gcc
sudo pip install wxpython
Building the program is as easy as running make:
make && sudo make install