This patch disables display driver in u-boot which improves EDID detection
https://forum.armbian.com/topic/13651-pine-a64-no-hdmi-signal/?do=findComment&comment=99169

diff --git a/configs/Cubieboard_defconfig b/configs/Cubieboard_defconfig
index 17b0a758..eb6d29c9 100644
--- a/configs/Cubieboard_defconfig
+++ b/configs/Cubieboard_defconfig
@@ -15,3 +15,4 @@ CONFIG_SUN4I_EMAC=y
 CONFIG_SCSI=y
 CONFIG_USB_EHCI_HCD=y
 CONFIG_USB_OHCI_HCD=y
+CONFIG_VIDEO_DE2=n