I will introduce arguably the simplest extension of the Standard Model which leads to renormalizable long-range vector-mediated neutrino self-interactions. Exploring bounds on the parameter space, we will see that there are unconstrained regions with four-neutrino intractions of a strength similar to what has been discussed to resolve the cosmological Hubble tension. The extended gauge and scalar sectors lead to signatures in invisible Higgs and Z decays, thereby relating the Hubble tension to precision measurements at the LHC and future colliders. Curiously, the model requires hidden neutrinos in a mass and mixing range suitable to resolve short baseline neutrino oscillation anomalies via the "decaying sterile neutrino solution". Finally, time permitting, i will discuss how decaying sterile neutrinos can explain the highest-ever-observed photons from gamma ray bursts of energies 18TeV and 251TeV emitted from the recently brightest-ever-observed GRB 221009A.