I'm using Raspberry Pi 3 Model B Rev 1.2 with Raspbian Stretch installed. I can't use the on board WiFi adapter. Clicking on the WiFi icon on the task bar shows 'No wireless interfaces found'.
sudo ifup wlan0" shows "ifup: unknown interface wlan0".
Running the ifconfig and ifconfig -a commands and "sudo nano /etc/network/interfaces" shows the following.
I noticed that in RPi B+ model running on a fresh install of Raspbian Stretch OS , I can use WiFi. But I cannot do the same on a RPi B model with a fresh install of Stretch. This happens on other B+ and B model devices as well.