We present the first results obtained from the S${}^3$ Low-Energy Branch, the gas cell setup at SPIRAL2-GANIL, which will be installed behind the S${}^3$ spectrometer for atomic and nuclear spectroscopy studies of exotic nuclei. The installation is currently being commissioned offline, with the aim to establish optimum conditions for the operation of the radio frequency quadrupole ion guides, mass separation and ion bunching, providing high-efficiency and low-energy spatial spread for the isotopes of interest. Transmission and mass-resolving power measurements are presented for the different components of the S${}^3$-LEB setup. In addition, a single-longitudinal-mode, injection-locked, pumped pulsed-titanium–sapphire laser system has been recently implemented and is used for the first proof-of-principle measurements in an offline laser laboratory. Laser spectroscopy measurements of erbium, which is the commissioning case of the S${}^3$ spectrometer, are presented using the $4f^{12}6s^2$${}^3{H}_6\to 4f^{12}{(}^{3}H)6s6p$ optical transition.