CubicSDR is a strong, growing open source SDR GUI. CubicSDR supports a wide variety of SDR devices including:
- Red Pitaya
and many more via SoapySDR library.
CubicSDR is targeted for desktops and laptops–the CubicSDR GUI is beautiful, but takes more resources than earlier SDR GUIs.
CubicSDR is available for Ubuntu and Debian simply by:
apt install cubicsdr
See the main window description to note that you must click on the waterfall to add a “modem”, the volume of which is adjusted by the bar on the upper right. Be sure the “M” mute button is NOT highlighted.
For those with other Linux versions, you can compile from source.
The Raspberry Pi 3 can run CubicSDR–barely and with some hacking.
Related: Quickstart RTL-SDR on Linux