In https://wiki.debian.org/Bumblebee#Debian_10_and_older I've found this hint:
```
[ERROR]Cannot access secondary GPU - error: [XORG] (EE) No devices detected
You may have to set the BusID manually, in /etc/bumblebee/xorg.conf.nvidia. To get the BusID, run lspci | egrep 'VGA|3D'
in a terminal. Refer to the comments in that file for further instructions.
```
So I've edited `/etc/bumblebee/xorg.conf.nvidia` and uncommented one line so
it's now:
```
BusID "PCI:01:00:0"
```
And it works!
`lspci | egrep 'VGA|3D'` on my machine returns:
```
00:02.0 VGA compatible controller: Intel Corporation 4th Gen Core Processor
Integrated Graphics Controller (rev 06)
01:00.0 3D controller: NVIDIA Corporation GM107M [GeForce GTX 860M] (rev ff)
```
So some part fails to detect that only NVIDIA card..? :)
