dpapavas

I never said it didn't, but one still has to read up on how it works, how to get it to compile just the kernel, after applying patches, how to use that kernel and handle unbootable systems etc.;  that sort of thing.  I'm very new to Armbian.
 
 
I meant that, since you're currently working on getting the Media Framework to work based on the mainline kernel and asssuming that this HDR issue is, at least in part, due to something missing from the kernel, whether it might be better to troubleshoot this in the mainline version of the Media Framework.  But read also below.
 
 
I sort of managed to do the reverse: find a libreelec setting that makes HDR output not work and exhibits the same behavior I get on Armbian.  As far as I can see, librelec for rockchip devices doesn't apply any KODI patches (although there is this).  I'm not sure if that means that the plain/unmodified source is used for KODI, or whether some patches are applied regardless of board, but on librelec, KODI has an extra option that lets you select the "HDMI output format".  This essentially sets the color space to RGB or YCbCr (4:2:2 or 4:4:4 ).  The display only switches to HDR with the (default) YCbCr mode, not with RGB.
 
The Media Framework version of KODI is missing that option.  In fact I haven't found any reference to it, outside of libreelec.  Output seems to default to RGB colorspace, as can be seen with:
 
 
In contranst in librelec, I get something like:
 
 
I'm not sure of course, that getting KODI to switch to a YUV HDMI output mode will be enough to make the display switch to HDR, but it seems worth trying, especially since it should be easier than semi-blindly applying kernel patches.  That said, I can't seem to find much info on how to do so.  Let me know if you have any insight to share.