You could also buy the DVD/Blu-Ray/UHD and rip it...
I've heard it repeated many times over the years that movie torrent sites are a magical one-stop shop where every movie in the history of cinema is available instantly and in full quality, but I've just never seen it except for new release stuff. Now perhaps the story changes a little with private trackers, but in order to use those you have to be an active seeder. Now you've moved from a simple DMCA bypass to actively distributing pirated content. Thanks, but I think I'd rather rip purchased movies onto my Plex server.
On the most popular Russian public torrent tracker, there are 22 results for that right now, and even though none of them are UHD, top two of the highest-bitrate 1080p BDRip torrents do have active seeders.
And, movies this old in 4k HDR, that's a thing? I can understand the 4k part, that at least can be done by scanning the original film at a higher resolution, but HDR? Doesn't it need to be shot in HDR to begin with?
From my experience due to DHT there are actually more seeders than listed on the site. I didn't have any trouble getting even quite obscure films.
I'd be surprised if more than 3% of the viewing population cared about this much resolution. You also can't torrent a reel of film, so dudes with private film screening rooms are screwed.
For science it took me 10:57 to locate, download, and extract a 45,215MB remux of Django (1966) from USENET.
But there must be some sort of re-encoding going on there. Because the copy of Django I ripped myself is 61.5GB, and it's only video and one DTS audio track. So I would put money on the copy you found being re-encoded somehow.
Here's a selection of releases for the movie Django (1966): http://rarbg.to/torrents.php?imdb=tt0060315