Hey Mario, OP here. Indeed, DIY guides are badly lacking in this domain. We are preparing a thorough benchmark of existing microphone array solutions. It will feature the ReSpeaker, Conexant, Matrix Creator, MicroSemi and MiniDSP which are all built for 360-degrees far-field audio capture. The goal is to have an excellent, affordable, and replicable hardware setup on par with Alexa and Google. Stay tuned!