Nvidia MX150 with Bumblebee on Debian Testing (Buster)

I recently bought a Dell inspiron 15 7000 notebook with Nvidia MX150 and a second intel card:

$lspci -nn | egrep -i "3d|display|vga"
00:02.0 VGA compatible controller [0300]: Intel Corporation Device [8086:3ea0]
01:00.0 3D controller [0302]: NVIDIA Corporation GP108M [GeForce MX150] [10de:1d10] (rev ff)

I’m using debian testing and given the optimus technology I installed Bumblebee and mesa utils (I followed the official debian doc here):

sudo apt-get install bumblebee-nvidia primus

Running the glxgears -info command everything is ok, the window appears with the gears turning. But if instead I launch glxgears with optirun, nothing happens, no errors, and the window with gears does not open:

optirun --debug -vv glxgears -info
    [  860.333401] [DEBUG]Reading file: /etc/bumblebee/bumblebee.conf
    [  860.334195] [DEBUG]optirun version 3.2.1 starting...
    [  860.334225] [DEBUG]Active configuration:
    [  860.334232] [DEBUG] bumblebeed config file: /etc/bumblebee/bumblebee.conf
    [  860.334239] [DEBUG] X display: :8
    [  860.334246] [DEBUG] LD_LIBRARY_PATH: /usr/lib/x86_64-linux-gnu/nvidia:/usr/lib/i386-linux-gnu/nvidia:/usr/lib/nvidia
    [  860.334254] [DEBUG] Socket path: /var/run/bumblebee.socket
    [  860.334261] [DEBUG] Accel/display bridge: auto
    [  860.334267] [DEBUG] VGL Compression: proxy
    [  860.334278] [DEBUG] VGLrun extra options: 
    [  860.334285] [DEBUG] Primus LD Path: /usr/lib/x86_64-linux-gnu/primus:/usr/lib/i386-linux-gnu/primus:/usr/lib/primus:/usr/lib32/primus
    [  860.334383] [DEBUG]Using auto-detected bridge primus
    [  861.162170] [INFO]Response: Yes. X is active.

    [  861.162180] [INFO]Running application using primus.
    [  861.162271] [DEBUG]Process glxgears started, PID 2639.
    [  861.171160] [DEBUG]SIGCHILD received, but wait failed with No child processes
    [  861.171175] [DEBUG]Socket closed.
    [  861.171189] [DEBUG]Killing all remaining processes.

I do not think there are errors …
This is the optirun and bbswitch state:

$optirun --status                     
Bumblebee status: Ready (3.2.1). X inactive. Discrete video card is off.

$cat /proc/acpi/bbswitch           
0000:01:00.0 OFF

If I run something randomly with optirun, like Firefox and re run the above commands:

Shell1:

optirun firefox

Shell 2:

$optirun --status        
Bumblebee status: Ready (3.2.1). X is PID 2908, 1 applications using bumblebeed.

$cat /proc/acpi/bbswitch 
0000:01:00.0 ON

it seems that with Firefox (a random thing) launched with optirun Bumblebee is active …

Can I therefore deduce that it is a glxgears problem that does not appear, but is everything well configured? Or something is wrong?

Can you advise me some tests to do?