Fix the “Bluetooth is turned off” error in Windows 10 Boot Camp (on a Mac)

When I booted my Mac into Windows today, I noticed that Windows spent a loooong on the loading spinner during boot. Then when I had finally logged in, I couldn’t use my Bluetooth devices because “Bluetooth is turned off”. Weird.

After some googling and numerous restarts and updates and trial & error... I discovered this One Simple Trick™️ to solving it:

Boot into macOS, turn on Bluetooth, then restart and boot into Windows.

For some weird reason, you need to enable Bluetooth in macOS. Otherwise, Windows get confused. I don’t understand how a macOS setting could affect the Bluetooth chip’s function when booted into a different operating system... but hey, it works.