This image https://chewitt.libreelec.tv/testing/LibreE…-12.95.1.img.gz has the following patch applied:
Diff
diff --git a/projects/Generic/linux/linux.x86_64.conf b/projects/Generic/linux/linux.x86_64.conf
index 0bd90b1804..68693c1f5e 100644
--- a/projects/Generic/linux/linux.x86_64.conf
+++ b/projects/Generic/linux/linux.x86_64.conf
@@ -4081,8 +4081,8 @@ CONFIG_CEC_NOTIFIER=y
#
# CEC support
#
-# CONFIG_MEDIA_CEC_RC is not set
-# CONFIG_MEDIA_CEC_SUPPORT is not set
+CONFIG_MEDIA_CEC_RC=y
+CONFIG_MEDIA_CEC_SUPPORT=y
# end of CEC support
CONFIG_MEDIA_SUPPORT=m
@@ -4957,7 +4957,7 @@ CONFIG_DRM_CLIENT_DEFAULT="fbdev"
CONFIG_DRM_LOAD_EDID_FIRMWARE=y
CONFIG_DRM_DISPLAY_HELPER=y
-# CONFIG_DRM_DISPLAY_DP_AUX_CEC is not set
+CONFIG_DRM_DISPLAY_DP_AUX_CEC=y
# CONFIG_DRM_DISPLAY_DP_AUX_CHARDEV is not set
CONFIG_DRM_DISPLAY_DP_HELPER=y
CONFIG_DRM_DISPLAY_DSC_HELPER=y
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See if that works? - Note that DP/USB-C adapters need to be an 'active' type that supports CEC tunnelling; and even then there's no guarantee that the CEC pin has been physically wired up.