On my 2008 e11 I have to mess with the buttons on the steering wheel to display it, unless it is below about 3 degrees, when it comes on by itself in case I didn't notice having to scrape ice off the windows.
I have the display that shows the clock all the time and one selectable other thing only.
The op says he has a 2016 E12, so he should see the outside temp permanently displayed to the far right of the speedo..... Unless it's faulty.
Thankfully mine was showing 24° yesterday. I did the sensible thing when arriving home by taking a chilled beer onto the patio. Guess I'll do the same today.