Flickering issues after fresh install on an Intel mini pc

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):

Note: Fresh install of Kubuntu doesn’t suffer the same issue…

Please, provide more details of your system.

Software: fresh install of Manjaro KDE Plasma (20.2)
Hardware: Beelink Gemini X45 http://bee-link.com/portal.php?mod=view&aid=113

CPU: Intel Gemini Lake Celeron J4105
Graphics: Intel HD Graphics 600
Storage: 128GB SSD

HDMI output to an Asus VS24A 1900x1200

Anything else I should share to help understand the issue?