You can't play UHD discs with PowerDVD on AMD systems. That's the grim, fatalistic news I got about an hour ago. It's new to me, but it's been a long time coming.
It's lost to the mists of time when Intel joined the BDA, but regardless, AMD never hopped on the bandwagon. We'll never be privy to the reasons AMD isn't a part of the consortium; could've been that negotiations fell through, could've been that there never were any negotiations, maybe they never thought to join, maybe AMD took a look at the streaming market and decided physical media was a lost cause, maybe the expense of paying into software development and lawyer fees wouldn't be worth the effort, maybe they have some kind of deal with Microsoft that makes producing parts for UHD-capable players and consoles a competitor to their own PC platforms, maybe they didn't want to give Intel anything they could use to get an edge on AMD, or maybe Intel put a sign outside the BDA treehouse that said "No AMD nerds allowed."
While we can speculate about why AMD isn't a part of the BDA, the end result is that there is legitimate consumer player software compatible with AMD PCs. There's a proprietary Intel instruction set called SGX; PowerDVD requires SGX in order to play UHD discs, which leaves AMD out in the cold. There's nothing inherently special about SGX aside from it being an Intel-exclusive technology; AMD has equivalent DRM protective instruction sets, but due to their lack of being in the cool kids clique, AMD's tech isn't whitelisted.
AMD might be missing out on who-knows-how-many millions of dollars in royalties from UHD Blu-ray and software sales, sales from AMD-based HTPCs, and long-term investor buy-ins, but who am I to question AMD's business decisions.
I know for instance that Play Ready 3 is not supported on the entire Vega series and you need this to play UHD on Netflix. I agree that if you are buying a card today for home theater the AMD card may not be the right choice. In fact integrated Intel graphics may even do a better job. That is a sad reality. Sorry you didn't know this apparently before your purchase. I don't get the WHY either.
Now if Power DVD is using an Intel only API then nobody can do anything about it, if Intel doesn't make it available to the market as a whole. I have no idea if they do or don't.
I have however as mentioned already ran into DRM that AMD does not support and Play Ready 3 for instance is available to all, AMD just doesn't support it on all cards. Polaris supports it but Vega does not and Vega is newer so go figure.
All I can say is you really gotta do your homework and don't assume anything when buying hardware these days.
One update on the situation, newest Intel CPUs dont have IntelSGX anymore, so its just a question of time until the requirement will be removed. But still talking about months or years.