EDIT I was told that this is the DV check (in your dmesg):
dv capability 6
SOCs with DV ability return value 7, any other value means no DV support.
I didn’t find anything on Google indicating the X96 Max Plus has DV licensing, so I’m not sure. I don’t know how to check other than booting Android and trying to play a DV video there.
You can try using the dovi.ko from Sabrina (Chromcast s905D3). It has a better chance of compatibility. I only know of this website hosting the entire firmware that you can extract it from. I’d start by checking Android, it’s less work.
The display can be set to DV in uboot, CE needs to know the uboot DV state (on/off) which you see tracked in dmesg. Some of the other stuff is the amdolby_vision module included with CE, and some of that is the s905x2 dovi.ko being loaded.
DV capability is determined by the SOC, so if it’s not DV certified there’s nothing CE can do to make it play DV videos.
-B is dolby audio licensing