Hi @chrfre,
did you already find a solution for setting the brightness?
I am using a TUXEDO Pulse 14 (AMD Ryzen 7 4800H, Radeon RX Vega, integrated graphics).
I also tried to set brightness using echo 12 | sudo tee /sys/class/backlight/acpi_video0/brightnes in dom0-Terminal which had no effect.
Using a Lubuntu live distro it worked flawlessly.
I also used Xfce Power Manager to set the “Handle display brightness keys” to “on” in the General tab => no effect at all.
Display is running full brightness killing my eyes.
One further issue: using an external monitor using the HDMI port does not work with this setup. I created a separate thread for that: HDMI: external monitor is not detected