Tunable field-linked s-wave interactions in dipolar fermi mixtures Spin mixtures of degenerate fermions are a cornerstone of quantum many-body physics, enabling superfluidity, polarons, and rich spin dynamics through s-wave scattering resonances. Combining them with strong, long-range dipolar interactions provides highly flexible control schemes promising even more exotic quantum phases. Recently, microwave shielding gave access to spin-polarized degenerate samples of dipolar fermionic molecules, where tunable p-wave interactions were enabled by field-linked resonances available only by compromising the shielding (due to experimental limitations). Here, we study the scattering properties of a fermionic dipolar spin mixture and show that a universal s-wave resonance is readily accessible without compromising the shielding. We develop a universal description of the tunable s-wave interaction and weakly bound tetratomic states based on the microwave-field parameters. The s-wave resonance paves the way to stable, controllable and strongly-interacting dipolar spin mixtures of deeply degenerate fermions and supports favorable conditions to reach this regime via evaporative cooling. 9 Springer Nature application/pdf