XDMCP with headless RPI4-aarch64

[hp4]

Hi,
I've installed a headless RPI4 with aarch64 some time ago and now want to access it via XDMCP. This works nice on another RPI4 with 32Bit.

But with aarch64 I'm not able to start the X-Server. Error message: /dev/fb0 not found.

All packages are uptodate.
kernel 5.10.10-1-ARCH #1 SMP Sat Jan 23 16:26:04 MST 2021 aarch64 GNU/Linux

I've found a lot of hints in the internet, but nothing works. I've learnt that RPI4 doesn't create a frame buffer during boot if no physical display is attached. So I've added "hdmi_force_hotplug=1" to /boot/config.txt but without success.

Can anybody help with creating framebuffers (/dev/fb0) during boot of headless devices ?
Is there any way to emulate a phyical display by creating a virtual display?
Or can I configure X-servers to run without screen only for XDMCP?

Any help or hints would be appreciated

[graysky]

Not sure about XDMCP but tigervnc works well.