The ambient-pressure superconductivity in ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ thin films via compressive epitaxial strain provides a highly accessible platform for diverse characterization techniques, facilitating the studies of high-temperature superconductivity. Here, we systematically map the phase diagram and reveal the superconducting dome with an electron-hole crossover in compressively strained ${\mathrm{La}}_{3-x}{\mathrm{Sr}}_x{\mathrm{Ni}}_2{\mathrm{O}}_{7-\delta }$ thin films by simultaneously tuning Sr doping and oxygen content. The maximum transition temperature ($T_c$) coincides with an anomalous sign change in the Hall coefficient ($R_H$), reminiscent of electron-doped cuprates, which may signal a Fermi surface reconstruction. Beyond the superconducting dome, a $\ln 1/T$ insulating regime and a $T$-linear resistivity regime are also resolved, resembling behaviors observed in cuprates and infinite-layer nickelates. This work reveals a dome-shaped relationship between $T_c$ and $R_H$ and establishes a key framework for understanding unconventional superconductivity in nickelate systems.

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• Doping effects
• Superconductivity
• Nickelates
• Thin films
• Unconventional superconductors
• Molecular beam epitaxy