[NathanX]

 

I think this is a confusion between two uses for 'tone mapping'

The OP you quote is, I believe, talking about having an HDR display that benefits from MaxCLL and MaxFALL metadata so that HDR content that falls outside their display capabilities can be tone mapped with an awareness of the content's light levels. (The tone mapping is done by the display, informed by the now-available metadata)

I am guessing that your use of Tonemapping is for playing HDR content on an SDR display, where Kodi/CE has to handle tone mapping a Rec 2020 PQ HDR10 source into a Rec 709 SDR (BT.1886 or power law gamma) output signal. This is a trickier job for Kodi - and there are multiple approaches that can be taken (Scene Light vs Display Light EOTF mapping, and different gamut mapping approaches are also possible)

My Sony X800 UHD Blu-ray player had a number of HDR->SDR settings and I couldn't every find an optimal choice for playing UHD HDR10 Blu-rays on a Rec 709 UHD SDR display. I ended up buying a new UHD HDR TV... 

You are quite right, i guess the OP did not mean the same kind of tonemapping than I do. And yes, you are right again, I was referring to HDR->SDR tonemapping. 

I can only imagine the wisdom and secrets behind HDR->SDR tonemapping! And yes, there will never ever be some HDR->SDR tonemapping which can replace a real hdr picture. But thing is: the actual tonemapping result now is just unwatchable, which is a pity. Funny thing is: if i turn of tonemapping, every BT2020 source really looks bright (actually too bright), but at least you can watch the movie and get the details of the picture. 
So summing up that means: wait and see if there are some improvements regarding Hdr to sdr tonemapping in CoreElec or simply buy an HDR capable projector, right?