The Microcalorimeter Arrays for a TRItium eXperiment, MATRIX is one of the core projects within the “Explore Dark Matter” proposal. This experiment has been conceived to search for a tiny kink in a high statistics and high energy resolution 3H spectrum calorimetrically meas-ured which can be related to the existence of keV sterile neutrinos mixing with active neutri-nos. Large arrays of low temperature metallic magnetic alorimeters, where each detector has a 3H activity of the order of 10 Bq enclosed in the absorber, will be read out using the microwave SQUID multiplexing technique. High statistics and high energy resolution measurements of the 3H spectrum present two main challenges: first is to demonstrate that 3H loaded detectors can achieve good performance in terms of energy resolution and time resolution, second is to provide a multiplexed readout scheme able to allocate enough bandwidth per channel and with a reduced additional noise. We propose to perform proof of concept experiments, able to set the basis for the development of the large scale experiment. Our aim is to characterize MMC with 3H enclosed in the absorber and determine the achievable performance and to develop an innovative RF multistage mixer board which offers noise optimized signal conditioning and coarse hannelization. A further activity is the development of a concept for a scalable and flexible data acquisition system as a backend for detector electronics of the MATRIX experiment.