[jubilex]

The problem is the tonemapping on the N2+ is not good. For example, Lord of the Rings 4k HDR is much duller than the old 1080p bluray version (with Coreelec's HDR>SDR set to On in Kodi). 

You could try the new Beta Kodi v19.0 Matrix release.
Maybe there is an updated Linux Kernel used that would output different results.

Isn't tonemapping handled by part of the SoC on AMLogic devices? I guess a newer kernel may have more AMLogic tweaks - but I thought HDR<->SDR and HDR10<->HLG etc. conversion was handled at the SoC level rather than in software  (due to the large amount of processing required - - or is that a false assumption? (You're converting a video stream of 15Gbs if you're tone mapping 3840x2160 60fps 4:4:4 10-bit content)

Or am I totally wrong?  I though that was why tonemapping differed between different AMLogic platforms in how it performed (as different SoCs implemented different algorithms to do so?)

You are right, that is how Coreelec is currently doing it, just a switch in System settings to turn on the hardware tonemapping. But it's so bad as to be useless.

When I switch the software algorithms on and off in Matrix beta on Windows, there is no noticeable spike or dip in CPU or GPU usage, so it doesn't *seem* to be something that would be too tough for N2+ to handle, I hope.

edit: Response on Coreelec forum: "It looks like it wasn’t implemented for GLES, only for OpenGL and D3D, so it’s not gonna work on any ARM devices." I don't know if he meant the existing code won't work on ARM or the whole thing is impossible on ARM.

If so that's a bummer and means I need to stick to buying only SDR media for the forseeable future.