You can certainly hide the SSID on Deco (M5, at least...)  In the Wifi settings, click on the Network Name (SSID) (as though to edit the field) and the screen will show Network Name, Password, and a switch labled "Hide this network from Wi-Fi lists".  switch this on to hide the SSID.

That said, hiding the SSID is generally considered a bad idea as all your connected devices then have to broadcast the SSID instead in order to connect to the network.  They will then continue to broadcast the SSID when they are away from your network and hunting for Wifi reception.  This makes them more vulnerable to AP spoofing attacks, and doesn't help your base station security as it can still be seen from the active traffic.  for reference, see:

https://www.howtogeek.com/howto/28653/debunking-myths-is-hiding-your-wireless-ssid-really-more-secure/

http://www.fixedbyvonnie.com/2014/08/3-reasons-why-hiding-wireless-ssid-bad-idea/

https://www.techjunkie.com/should-broadcast-wifi-ssid/