Controlling atom–photon interactions in engineered environments is central to quantum optics and emerging quantum technologies.
Non-Hermitian (NH) photonic baths, where dissipation fundamentally reshapes spectral and dynamical properties, provide versatile platforms
for such control. Here, we investigate the relaxation dynamics of a single two-level quantum emitter coupled to the edge of a semi-infinite dissipative bosonic lattice with uniform loss. Despite the simplicity of this bath, we uncover rich dynamical phase transitions, i.e., qualitative
changes in spontaneous-emission decay as system parameters are varied. In particular, we establish the existence of an optimal dissipative
environment for accelerated spontaneous emission. The phase transitions are traced to spectral restructuring of the resolvent, in some
cases governed by the coalescence of resonance states on the second Riemann sheet. We identify these coalescences as virtual exceptional
points (EPs) of resonance origin, providing a conceptual bridge with EP physics while highlighting distinctive features of infinite-dimensional
NH systems. More broadly, our results illustrate how the specific nature of dissipation—whether uniform losses, staggered losses, or
dephasing—can profoundly impact emitter relaxation, pointing to dissipation engineering as a versatile tool for quantum technologies.