Ubuntu mate 20 hp 255 g6 video flickers

Hi all, I have a problem with the video card of the hp 255 g6 notebook.

Distributor ID: Ubuntu
Description: Ubuntu 20.04.1 LTS
Release: 20.04
Codename: focal

the problem is that if I log in to the pc the images are very distorted and you can't see the windows.
if you go to the initial login screen, everything is fine.
if i log in with xrdp it displays fine.
if i go into video control panel it gives me unknown video
place the output of the tested comads
in software Update -> additional drver ,nothing appears
i have checked proprietary idriver.
inxi -Fz
Device-1: AMD Stoney [Radeon R2/R3/R4/R5 Graphics] driver: amdgpu
Display: x11 server: X.Org 1.20.8 driver: amdgpu,ati
unloaded: fbdev,modesetting,vesa resolution: 1364x768~50Hz
OpenGL: renderer: llvmpipe (LLVM 10.0.0 128 bits) v: 3.3 Mesa 20.0.5

this script was set at startup but did not solve the problem.

xrandr --newmode "1368x768_60.00" 85.25 1368 1440 1576 1784 768 771 781 798 -hsync +vsync
xrandr --addmode default "1368x768_60.00"
xrandr --output default --mode "1368x768_60.00"

can anyone help me?

I see the output device is default but in my case is VGA-0. My code if that helps you ...

xrandr --newmode "1280x1024_60.00"  109.00  1280 1368 1496 1712  1024 1027 1034 1063 -hsync +vsync
xrandr --addmode VGA-0 1280x1024_60.00
xrandr --output VGA-0 --mode 1280x1024_60.00

i tried to use vga-0 but it gives error.
I try the parameters thanks

your device might be different, xrandr should tell you the device.

I copied the command without seeing the CVT screen to a file for review. after i created the right commands in the script.
I managed to set the screen by giving the commands by heart. okay thanks