I am glad to see my desktop machine isn't being left behind with this. In stock LTS Ubuntu the default image viewer shows the Display P3 images as does Firefox. The thumbnail in the file browser also has the logo showing.
Not sure about Chrome as I set the color flags to be sRGB a long time ago as, compared to Firefox, colours in Chrome are unsatisfactory on Linux.
I also tried on a consumer grade laptop that runs the latest (19.04) Ubuntu with one of those glossy screens, definitely not designed for Display P3. This failed in Firefox, Chrome, Gimp but the thumbnail in the file browser came good. How come when the hardware isn't there for it?
It seems like 25% of the colours are missing with a lot of that being green, green being quite an important colour. It must be possible to have some creative fun with this. If you can get images that only kids can see on their phones but adults not see on their boring PCs then you could have some variant of 'satanic backmasking' going on.
'Satanic backmasking' was where you could hear stuff about Satan on Beatles records if you played them backwards, listening whilst stoned. Politicians bothered themselves about young minds being corrupted by such things back in the day.
Maybe DCI-P3 images can court a similar controversy, shame April Fools Day is a lame day of corporate gags where nobody is fooled, otherwise DCI-P3 is ripe for moral panic, terrorising the adults with another thing for them to get their politicians frenzied about.
I hope Chrome gets to do colour a bit better, to Firefox standards. Otherwise we will be with half the world's screens not showing all the colours. Although not the same gap as between colour and monochrome, it is a huge difference to anyone that works with colour and needs subtle colour variations.