<?xml version="1.0" encoding="utf-8" ?>
<advancedsettings version="1.0">
<!-- enable debug logging -->
<loglevel hide="false">1</loglevel>
</advancedsettings>
First, create /storage/.kodi/userdata/advancedsettings.xml with that ^ content so Kodi is in debug mode for logs.
Second, run "vainfo | paste" and share the URL.
Now two things to experiment with:
a) Force the HDMI connector colourspace profile to Broadcast RGB:
Any different? - run "pastekodi" and share the URL again.
b) Force Kodi to use the i965 driver profile:
Create /storage/.config/kodi.conf with that ^ content, then reboot and run "pastekodi" and share the URL again. Also run "vainfo |paste" and share the URL.
I'm not expecting to acomplish anything .. but we'll have more information to review.
EDIT: 3rd thing: Do you have a DP to HDMI connector? .. i.e. connect to the DP socket not an HDMI socket. It would be interesting to see if that changes anything. I'm also wondering if the board has native HDMI connectors or internally they are DP with an LSPCON chip providing HDMI .. in which case have you ever updated the BIOS and/or LSPCON firmware?