Hi folks,
I just want to document a simple solution here that would have saved me some headaches.
My problem: I did not manage to turn off the flight mode, which meant that WIFI and Bluetooth transmitters were constantly off.
I had just before done some modifications in UEFI/system BIOS and suddenly this happened. I reverted my UEFI changes but the problem persisted. I kept on searching for the root cause in the UEFI boot routines (WLAN and BT transmitter are part of one combined hardware) but that would not help. I had not touched the hardware kill switch for flight mode so I did not expect the problem there. But: I was wrong.
My UEFI modifications must have flipped/reset the state of the radio kill switch on my laptop (Dell Latitude 7490). Like many laptops, mine has a shared kill switch (you need to press Fn-key + another button in the top row of the keyboard). Often (like in my case) there is no status LED on these keys. After just pressing this simple button, I could switch OFF flight mode in the GUI as expected. (User Feedback could be improved here...)
So, long story short: After fiddling with UEFI/BIOS (which is the case also if you have just made a fresh installation of your operative system), always check the actual status of the HW-Flightmode Switch. Even if you have not actively touched it, its setting might have changed and the radio might be turned off.
Very simple really, but unexpected. If that only helped a single person, it was worth sharing this here.