How familiar are you with torrents? I can send you an invite to a private tracker full of 4k remux documentaries.. I just think you are better with 1080p if watching on a laptop. For me at least, I can't tell the difference (and I have a 4k screen on my laptop)

Try Real Debrid. It's rare to not find something. Should you really not be able to find them, then the news servers are where you should head next. Just about anything ever made is on nzb. You'll need to pay some money and do a little learning, but the Usenet is pretty rad once you figure it out. It's a lot easier now than it used to be too. They have clients that will search, download, unpack, and assemble, all at the click of a button. But like I said, Real-Debrid+Stremio+Torrentio is amazing.

My advice for finding torrents, so long as they are not insanely obscure, is using qbittorrent with tons of search plugins. It may be hard to find av1 but if you have a new GPU you can transcode quickly, or if you don't you can always use software encoding.