Have the same Problem, none of my Displays work.
On a iiyama 4k Display i get the Black Screen with a Mousecursor that freezes after 5 seconds.
On a Samsung T220 that is capable of 1680x1050 i get no Output at all.
The T220 only have VGA and DVI. I Use a DVI to HDMI Cable.
Output of modetest:
root@starfive:~# modetest -M starfive -c
Connectors:
id encoder status name size (mm) modes encoders
116 115 connected HDMI-A-1 470x300 1 115
modes:
index name refresh (Hz) hdisp hss hse htot vdisp vss vse vtot
#0 640x480 59.94 640 656 752 800 480 490 492 525 25175 flags: nhsync, nvsync; type: driver
props:
1 EDID:
flags: immutable blob
blobs:
value:
00ffffffffffff004c2de50332325754
20120103802f1e782aee91a3544c9926
0f5054bfef80b30081808140714f0101
0101010101017c2e90a0601a1e403020
3600da281100001a000000fd00384b1e
510e000a202020202020000000fc0053
796e634d61737465720a2020000000ff
00483958513830373632380a20200025
2 DPMS:
flags: enum
enums: On=0 Standby=1 Suspend=2 Off=3
value: 0
5 link-status:
flags: enum
enums: Good=0 Bad=1
value: 0
6 non-desktop:
flags: immutable range
values: 0 1
value: 0
4 TILE:
flags: immutable blob
blobs:
value:
I tried several options in /etc/lightdm/lightdm.conf
[Seat:*]
#display-setup-script=xrandr -s 1920x1080
#display-setup-script=xrandr -s 1680x1050
#display-setup-script=xrandr -s 1280x720
display-setup-script=xrandr -s 640x480
Board Revision is 1.3B and Firmware is 2.8.0
Latest debian image fully updated