Software-defined radios (SDRs) are indispensable for signal reconnaissance and physical-layer dissection, but despite we have advanced tools like Universal Radio Hacker, SDR-based approaches require substantial effort. Contrarily, RF dongles such as the popular Yard Stick One are easy to use and guarantee a deterministic physical-layer implementation. However, they're not very flexible, as each dongle is a static hardware system with a monolithic firmware. We present RFquack, an open-source tool and library firmware that combines the flexibility of a software-based approach with the determinism and performance of embedded RF frontends. RFquack is based on a multi-radio hardware system with swappable RF frontends, and a firmware that exposes a uniform, hardware-agnostic API. RFquack focuses on a structured firmware architecture that allows high- and low-level interaction with the RF frontends. It facilitates the development of host-side scripts and firmware plug-ins, to implement efficient data-processing pipelines or interactive protocols, thanks to the multi-radio support. RFquack has an IPython shell and 9 firmware modules for: spectrum scanning, automatic carrier detection and bitrate estimation, headless operation with remote management, in-flight packet filtering and manipulation, MouseJack, and RollJam (as examples). We used RFquack to setup RF hacking contests, analyze industrial-grade devices and key fobs, on which we found and reported 11 vulnerabilities in their RF protocols.