The native WiFi of the Raspberry Pi 3, limited to 2.4GHz band doesn't work well for me. It is very slow and unreliable. I need to connect to the 5GHz band of my WiFi router. I bought a USB-WiFi dongle and it is recognized by the system. But I couldn't find how to shut down the built-in WiFi and replace it with the USB dongle.
I either have to shut down the native WiFi and re-associate wlan0 with the USB dongle, or shut down wlan0 and activate l0 or eth0 with the USB dongle. All the posts I saw describe either how to install a USB dongle on an RPi other than rPi3 (that I know how to do) or troubleshoot the rPi3 with its native WiFi (I don't have that problem either, it does work but it is way too slow).
Thank you for any guidance.