after Lite install, unstable screen on old Asus x50SL

[LioS1959]

@stevef : hi again Steve, no the display is not stable when I boot the lve USB either; in fact, the behaviour is exactly the same when booting the live iso or the installed version.

the output from the 3 commands you suggested (from the installed version) is as follows :
 lionel  ~  1  sudo lshw -C display
[sudo] password for lionel:
*-display
description: VGA compatible controller
product: RV620/M82 [Mobility Radeon HD 3450/3470]
vendor: Advanced Micro Devices, Inc. [AMD/ATI]
physical id: 0
bus info: pci@0000:01:00.0
logical name: /dev/fb0
version: 00
width: 32 bits
clock: 33MHz
capabilities: pm pciexpress msi vga_controller bus_master cap_list rom fb
configuration: depth=32 driver=radeon latency=0 resolution=1280,800
resources: irq:24 memory:d0000000-dfffffff ioport:d800(size=256) memory:fdef0000-fdefffff memory:c0000-dffff
 lionel  ~  lspci | grep -i VGA
01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] RV620/M82 [Mobility Radeon HD 3450/3470]

inxi -Gx
Graphics:
Device-1: AMD RV620/M82 [Mobility Radeon HD 3450/3470] vendor: ASUSTeK
driver: radeon v: kernel arch: TeraScale bus-ID: 01:00.0
Device-2: Chicony 1.3 MPixel UVC Webcam driver: uvcvideo type: USB
bus-ID: 2-5:3
Display: x11 server: X.Org v: 21.1.11 driver: X: loaded: radeon
unloaded: fbdev,modesetting,vesa dri: r600 gpu: radeon
resolution: 1280x800~60Hz
API: EGL v: 1.5 drivers: kms_swrast,r600,swrast platforms:
active: gbm,x11,surfaceless,device inactive: wayland
API: OpenGL v: 4.5 compat-v: 3.3 vendor: mesa v: 25.0.7-0ubuntu0.24.04.2
glx-v: 1.4 direct-render: yes renderer: AMD RV620 (DRM 2.50.0 /
6.8.0-85-generic LLVM 20.1.2)
I'll send you the output from the same commands while running the live version in a bit, rebooting takes a while on this baby...