there really isn't SHIT for 4k content. BTN/IPT have some of the top tier TV shows from Netflix/amazon, the sizes are insanely huge though - like I just downloaded Narcos in 4K, its 140 gigs each season. I'm watching each episode and just deleting it, its too big to keep around. I prefer to download even though i have netflix, prefer using my PC as a decoder instead of the TV netflix app which I don't know what the VBR is its streaming at.
I rarely find movies in 4K. For example John Wick 2 is out on 4k bluray in USA, I actually own the UHDs, but i am sorta too lazy to rip it so was hoping to find a download. Nope. Same with wonder woman and GOTG2, although I'm not sure its out in 4k in NA. IPT has a few 4k (search for 2160p in movies category, 99% of 2160p are porn torrents) but its mostly shitty movies I wouldn't watch again.
At this point I'm resigned to keeping my movie library in 1080p with the occasional purchase of a 4k bluray. I do have a PTP account but haven't delved deep into that site, don't know of any sites that specialize in 4K rips that are kept only on that site - anything popular would make its way to IPT quickly.
Even finding Planet Earth II is tough, there is only one 4k RIP of it and the default language is FUCKING RUSSIAN. Jesus Christ.