Manjaro KDE 20.2.
I tried installing multiple times, same issue: all good during the install session on the USB stick, but as soon as it reboots on the new system, the screen keeps flickering.
The machine is a Beelink X45 based on Intel Gemini CPU with integrated HD 600. That should be pretty standard hardware.
Video illustrating the issue (fast forward to 1:40):
youtu.be/uEuYNq0Gkww