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/Cubieboard2_defconfig b/configs/Cubieboard2_defconfig
index 292ce818..4d537bc2 100644
--- a/configs/Cubieboard2_defconfig
+++ b/configs/Cubieboard2_defconfig
@@ -18,3 +18,4 @@ CONFIG_SCSI=y
 CONFIG_USB_EHCI_HCD=y
 CONFIG_USB_OHCI_HCD=y
 CONFIG_MMC_SUNXI_SLOT_EXTRA=2
+CONFIG_VIDEO_DE2=n