A measurement of the CKM angle $\gamma$ is performed by applying a novel, unbinned, model-independent approach to datasets of electron-positron collisions collected by the BESIII experiment and proton-proton collisions by the LHCb experiment, corresponding to integrated luminosities of 8 fb${}^{-1}$ and 9 fb${}^{-1}$, respectively. The $CP$-violating phase $\gamma$ is determined from ${B^{\pm}\rightarrow D(\rightarrow K^{0}_{\rm S} h^{\prime+}h^{\prime-}) h^{\pm}}$ decays in LHCb data, where $h^{(\prime )}$ is either a pion or kaon, while the corresponding strong-phase parameters are measured using doubly tagged ${D\rightarrow K_{\rm S/L}^0 h^{\prime+} h^{\prime-}}$ decays in the quantum-correlated $D\overline{D}$ system present in BESIII data. A joint fit to both datasets, which allows for a simultaneous determination of the associated $CP$-violating observables and strong-phase parameters, yields $\gamma =(71.3\pm 5.0{)}^{\circ }$. The result is the most precise to date and consistent with previous measurements and world averages.