Beta Convergence edition external display?

[Ferenc]

In the meantime I have been pointed to the even newer blog entry about the topic: https://xnux.eu/log/#039

DRI state seems OK

Code:

grep -A3 HDMI-A-1  /sys/kernel/debug/dri/1/state
connector[52]: HDMI-A-1
        crtc=(null)
        self_refresh_aware=0

But still the output can't be turned on:

Code:

wlr-randr --output HDMI-A-1 --on
unknown output HDMI-A-1

The 

Code:

received SVID

etc, then suggest that it's not a hardware fault, but perhaps a kernel?