The design and experimental demonstration of a 16-channel frequency-domain multiplexing (FDM) read-out for transition-edge sensor bolometers is presented. This MUX electronics is intended to read out the 326 spiderweb bolometers of the LSPE/SWIPE balloon-borne experiment, which aims at the detection of the B mode polarization of the cosmic microwave background at large angular scales. The cryogenic part of our 16-channel FDM read-out chain features LC resonators composed of custom Nb superconducting inductors and surface mount device ceramic capacitors mounted on boards next to the detector wafers, at 300 mK, while the superconducting quantum interference device board is at 1.6 K. The warm section is based on a modular solution, with mezzanine plug-ins for digital-to-analog converters, analog-to-digital converters and a system-on-chip (based on the Altera Cyclone V field programmable gate array). The warm electronics handles the generation of the FDM tones, the de-multiplexing and the digital signal analysis including, e.g. cosmic ray glitches removal. Here, we recall its specifications, we address noise considerations, and finally we present the latest results obtained using flight models of our custom-designed boards.