Sage is a project working on creating geographically distributed sensor systems including cameras, microphones, weather and air quality stations in order to benefit the work of scientists. Recently on their GitHub they have uploaded a Jupyter Notebook showing how they have used an RTL-SDR V3 on a Linux Laptop to analyze lightning discharges. When lightning strikes, it creates a broadband RF pulse generally across the lower frequencies. This is how live lightning maps like Blitzortung work.

In their example Sage use a dipole antenna and analysis frequency of 30 MHz. The notebook doesn't offer much additional information, but provides Python Numpy and Scipy code which can be used to detect and plot the lightning pulses.