The extragalactic radio background is an almost isotropic low-frequency glow that remains after subtracting Galactic emission and resolved radio sources, and measurements such as ARCADE 2 report an amplitude and spectral slope significantly higher than expected from known source populations (Fixsen et al. 2011; Seiffert et al. 2011). Within ΛCDM, explaining this excess without overproducing source counts, violating gamma-ray and 21 cm constraints, or invoking finely tuned exotic dark-sector mechanisms has proven difficult, leaving the true origin of the radio background tension between standard astrophysics and new physics scenarios (Cooray 2016; Fornengo et al. 2014).