In this talk we presented a minimal gauge extension of the Standard Model that simultaneously addresses proton stability, neutrino masses, baryogenesis and a light pseudo-Nambu-Goldstone boson (the majoron) as a dark-matter candidate. The extension is based on a single extra $\mathrm{U}(1)$ gauge symmetry, two singlet scalars that break it, and three right-handed neutrinos required by anomaly cancellation. We summarise the symmetry-breaking pattern that enforces exact proton stability at low energies, describe the resulting neutrino mass textures and their implications for neutrinoless double-beta decay, characterise the majoron and its cosmological production channels, and outline the most relevant experimental and observational probes.