Google hacked version of flash player for Kit Kat. With dolphin browser you can enable flash content with this.
But not in Flipboard, which embeds a lot of video into articles. I can break out of Flipboard and into dolphin, then load the file that way but it's a much better experience on my 4.2 device which can simply load the video.
The experience is similar with other apps that embed links.
Oh, and of course I'd forgotten - the magazine UI is basically flipboard, so it must spend a lot of time *trying* to show video and being unable to, because so much video out in the world won't work with Kitkat, or barely wll at best.
New hardware often requires new software. The tab pro 8.4 is a dual dsi device that is on the bleeding edge of what is supported.
Pardon my ignorance, but what is dual DSI?
I understand that the n-1 support is difficult, especially given how long folks often have to lobby to get source code. I still empathize with the OP, though - if I want to run an older linux on newer hardware, I very often can. I may sacrifice a feature or three, but it would be nice if Android supported doing that as well.
I will be shocked if anyone tries
There's the thing - as far as I know, folks with build tools and knowhow aren't that interested in trying.
My impression is that it's ultimately down to the difficulty of getting source for hardware drivers, to support building without dependencies on newer system features. A lot of times, though, it's expressed along the lines of "what idiot would want to do that?" - and the transition to Kitkat is starting to highlight some areas where the newer OS seems incremental at best, and for many, purely lateral.