Not being on Roku's kinda weird, as it's hugely popular, widely deployed, and sees high usage. It's an odd platform but if your product is a video streaming catalogue + service well, that's exactly what it's built to do and getting that going's not all that hard.

But maybe they're looking for access to whatever special SDK the big boys (Netflix, Google) get so they can make their branding folks happy (more consistency with experience on other platforms). I'd imagine developing with that's more involved.

Samsung, some kind of custom Android probably? TV operating systems are a pain in the ass to test, fairly expensive to develop for, and relatively bad at drawing actual usage no matter how widely they're deployed. Might be the delay there. Big enough service needs to pay attention to that junk eventually, but I could see them dropping that for launch.