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/Cubietruck_defconfig b/configs/Cubietruck_defconfig
index 88b3322e..5cfcc06a 100644
--- a/configs/Cubietruck_defconfig
+++ b/configs/Cubietruck_defconfig
@@ -29,3 +29,4 @@ CONFIG_USB_EHCI_HCD=y
 CONFIG_USB_OHCI_HCD=y
 CONFIG_USB_MUSB_GADGET=y
 CONFIG_MMC_SUNXI_SLOT_EXTRA=2
+CONFIG_VIDEO_DE2=n