Software-defined radio app
There is a surprisingly big amount of amateur radio operators, radio listening enthusiasts and/or hobbyists among Linux and GNOME users. One of the most popular things among these groups in last 15 years is called "software-defined radio". It is "a radio communication system where components that conventionally have been implemented in analog hardware (e.g. mixers, filters, amplifiers, modulators/demodulators, detectors, etc.) are instead implemented by means of software on a personal computer" (source). In practice, it means that (for example) a cheap, small USB dongle can be used as an advanced wideband receiver offering many features that even expensive, hi-end hardware receivers do not usually have. For example a "waterfall display" for visual representation of received signals.
There are many high-quality and good looking software-defined radio apps available for both Windows and macOS platforms. This is how such app can look like. In contrast, this is how one of the best SDR apps available for Linux do look like. There is no SDR app with a good looking GUI that ideally adheres to the GNOME Human Interface Guidelines available for Linux. It would be amazing if there was such app available.