I have purchased, recommended and installed dozens of Deco M5 units. They provide very good range and performance in a small unit. Unfortunately TP-Link updated the app and changed core functionality:

I recently configured three Deco M5s in a network and turned 2.4Ghz off. I do not see the M5 2.4Ghz SSID, however, wifi sniffers detect multiple hidden signals on channel 9. These are from the Deco M5