I found the issue, I guess
DietPi-Software
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Step: Installing X.Org X Server: aka X11 - X Window System implementation
/boot/dietpi/dietpi-software: line 2666: /etc/X11/xorg.conf.d/02-dietpi-rpi5.conf: No such file or directory
[ OK ] DietPi-Software | cd /tmp/DietPi-Software
Directory /etc/X11/xorg.conf.d/
did not exist and would need to be created beforhand.
PR up: DietPi-Software | X-Server by Joulinar · Pull Request #7056 · MichaIng/DietPi · GitHub