Measuring the total neutrino mass is one of the most exciting opportunities available with next-generation cosmological data sets. We study the possibility of detecting the total neutrino mass using large-scale clustering in 21cm intensity mapping and photometric galaxy surveys, together with CMB information. We include the scale-dependent halo bias contribution due to the presence of massive neutrinos, and use a multi-tracer analysis in order to reduce cosmic variance. The multi-tracer combination of an SKAO-MID 21cm intensity map with Stage~4 CMB lensing dramatically shrinks the uncertainty on total neutrino mass to σ(Mν)≃45meV, using only linear clustering information (kmax=0.1h/Mpc) and without a prior on optical depth. When we add to the multi-tracer the clustering information expected from LSST, the forecast is σ(Mν)≃12meV.