“…On the other hand, the milestone work of Braak revealing the integrability [ 3 ] of the quantum Rabi model (QRM), [ 17 ] which is a most fundamental model of light‐interactions, has triggered an intensive dialogue between mathematics and physics [ 18 ] and leads to a boom of theoretical developments. [ 4,5,19–63 ] Without mentioning the ubiquitous role of light‐matter interaction and its broad relevance to quantum optics, quantum information and quantum computation, [ 1,64–67 ] quantum metrology, [ 36–38,68 ] condensed matter, [ 2,27,28 ] and relativistic systems, [ 69 ] the explosively‐growing investigations have yielded abundant findings in the QRM and its extensions, such as hidden symmetry, [ 60–63 ] various patterns of symmetry breaking, [ 26,27,29 ] few‐body quantum phase transitions, [ 5,22–29,70 ] multicriticalities and multiple points, [ 26–28 ] universality classification, [ 24,25,27,52 ] spectral collapse, [ 33–35,45,48 ] photon blockade effect, [ 39,40 ] spectral conical intersections, [ 42 ] classical‐quantum correspondence, [ 41 ] single‐qubit conventional and unconventional topological phase transitions, […”