Gfilui

I'm having an issue with my laptop's built-in screen.

The boot screen with the laptop's brand logo and the BIOS key doesn't appear when I turn on the computer. The screen is blank, and after a few seconds, I can see the OS booting on the screen.
When I connect an HDMI screen, I can see the brand's logo on it.

The problem appeared on Ubuntu 17.04 in November.

I tried to make a fresh install of Ubuntu 16.04 (I had to do all the install with the HDMI screen), and now even the OS isn't displayed on the built-in screen. When I check the Ubuntu displays settings, I can only see the HDMI display.

$ xrandr -q
Screen 0: minimum 320 x 200, current 1920 x 1200, maximum 8192 x 8192
DP-1 disconnected (normal left inverted right x axis y axis)
HDMI-1 connected primary 1920x1200+0+0 (normal left inverted right x axis y axis) 518mm x 324mm
 1920x1200 59.95*+
 1920x1080 60.00 50.00 50.00 50.00 59.94 
 1920x1080i 60.00 50.00 59.94 
 1600x1200 60.00 
 1280x1024 75.02 60.02 
 1440x900 74.98 59.90 
 1280x800 74.93 59.91 
 1280x720 60.00 50.00 59.94 
 1024x768 75.03 70.07 60.00 
 800x600 72.19 75.00 60.32 56.25 
 720x576 50.00 
 720x576i 50.00 
 720x480 60.00 59.94 
 720x480i 60.00 59.94 
 640x480 75.00 72.81 66.67 60.00 59.94 
 720x400 70.08 

I tried to activate the DP-1 display with the command

$ xrandr --output DP-1 --auto

I also check that all the firmwares of the i915 driver were presents:

$ ls /lib/firmware/i915/ | grep kbl
kbl_dmc_ver1_01.bin
kbl_dmc_ver1.bin
kbl_guc_ver9_14.bin
kbl_huc_ver02_00_1810.bin

My config:

OS: Ubuntu Gnome 16.04.5
Kernel: 4.15.0-29-generic
CPU: Intel KabyLake i7 7500U
GPU: Intel HD Graphics 620

I hope the question is clear, it's a hard situation to explain so ask me if more informations are needed.

Thanks for your help!