If the remnant core mass is between 1.4 and 3 solar masses after collapse, what does it stabilize as?

An incredibly dense neutron star.

The ultimate fate of the collapsed stellar core is determined by the remaining mass after the outer layers have been blown away by the supernova. If the mass of this remnant core falls within a specific range, generally cited between approximately 1.4 solar masses (the Chandrasekhar limit) and up to about 3 solar masses, the collapse halts when the core achieves neutron degeneracy pressure. This pressure, exerted by the tightly packed neutrons resisting further compression, is sufficient to stabilize the remnant against its own gravity. The resulting object is a neutron star, an exotic body characterized by extreme density, where the mass of the Sun is squeezed into a sphere only a few kilometers wide.