Software-defined radio receiver application built on GNU Radio with a web-based UI and plugins. In development, usable but incomplete. Compatible with RTL-SDR.
Installation docs: https://shinysdr.switchb.org/manual/installation
Claims that it requires more horsepower than a RasPi can provide. Remains to be seen.
Written using Python v2.7. Don't think it's been updated to Python3 yet.