Linux

If it's a "disturbing" video it's probably required to login to "prove" you're an adult or some bullshit like that. Those tools would need a way to authenticate as such.

Won't play for me either, I tried Firefox and Vanadium (chromium variant). Screw meta.

I would guess that it's probably not viable. Like, the problem isn't that a tool isn't processing the webpage correctly, but rather that the website isn't actually giving access to the video at all unless you sign in.

In general, if you can view a video but just not download it, Firefox (using the desktop UI) will let you the URL of the video. You click on the lock icon by the URL bar -> Connection Secure -> More information -> Media. This also lets you download images and so forth that have ad-hoc website-level "DRM" and try to make it difficult to download images. cough Pinterest.

Someone could create a service that logs in and then proxies the request, but I imagine that Threads would kill the account they're using

I expect that they want to disallow video streams to not-logged-in users, or they wouldn't have done what they did.

One thing that could maybe be done technically is for some service to do a fuzzy hash of each frame of videos

kind of like TinEye does for static images

and then given a static frame like this, lists all the videos that it has indexed that contain something that looks like that frame. Assuming that some service hasn't already started providing something along those lines. But that'd probably require more processing power, bandwidth, and storage than someone like TinEye is using, as I bet that there is more data going up to the Internet in the form of video frames than of static images.

EDIT: I do see other videos further down in the thread playing. So not-logged-in viewers can see some video content, just not that. Hmm.

That video has to be treated differently than the later videos

maybe it won't play without in-browser DRM support or the like? Or maybe it's above a certain size?

EDIT2: I don't think that it's in-browser DRM. I just checked, and WideVine works in Firefox on this test page. And your URL doesn't work in Firefox (or Chromium) on this system.

Maybe it could be some sort of new codec? I can't imagine that they wouldn't have a fallback, though.

EDIT3: This service can provide an mp4 link. Not sure if they're proxying it or just digging through the guts more than yt-dlp does:

https://threadster.app/download

EDIT4: It looks like the actual mp4 link I get is from a "threadster"-specific CDN account, so my guess is that they may well be proxying it, else I'd think that they'd just be linking to the video on Threads directly.

EDIT5: The downloaded .mp4

which may or may not be identical to the original video stream

has a size of 6216038 bytes, so if Threads is restricting it based on size, it's a pretty low restriction.

One other thing occurred to me. A number of services block "adult" content for some definition of "adult". This (a) conforms to laws in various jurisdictions about blocking children from seeing content, and (b) creates a hook to get people to create an account. YouTube, for example. It could be that Threads has flagged this as "not for children", so it requires an "adult" account to see the thing. I could very readily see some white supremacy group marching as qualifying as "adult" for one of those definitions.

EDIT6: It may be that Threads generates a unique video for each request, does a digital watermark or something, to try to track down what account entities like Threadster are using to pull videos from. Or it could be that Threadster is modifying the video. But I ran the video from from Threadster through rhash to generate a magnet URL, so if (a) neither service is modifying the video to make it distinct and (b) anyone has uploaded the file to a BitTorrent node with DHT enabled, then I imagine that this should get you to it; I generated a magnet URL for the file with all supported hashes.

$ rhash --magnet -a threadster_0ovs0ywp.mp4 
magnet:?xl=6216038&dn=threadster_0ovs0ywp.mp4&xt=urn:crc32:ce0986c6&xt=urn:md4:7f1b446dafac136ef41d7c8211a153b2&xt=urn:md5:af199305ebd27c6ff34e890d36374d37&xt=urn:sha1:qjyppsc27vuazq6zgyr4vflkumpour64&xt=urn:tiger:bff86af09fa62a93c35a67902ffbca9bdab5cf52f4d41baf&xt=urn:tree:tiger:vrk7ux5qrfzip24d7su4fjavdbj5iadh5i4le5q&xt=urn:btih:7d08a14e90712580809379ddf43778e1440c8ee1&xt=urn:ed2k:7f1b446dafac136ef41d7c8211a153b2&xt=urn:aich:qikeur6cwalyy4qokt62raheyvg7a7nc&xt=urn:whirlpool:4d6ae4d5ba366c6a0ed783efdff5371b7e969e03905952abcec3a8f398af4f5d5bdb81e9eb3c1c522ab336dab155dd89729c533ddbe8c0d00e7ad1b7e411331b&xt=urn:ripemd160:6067eae597a4a5a0c077b8b934bd0609dcffbdb1&xt=urn:gost94:83e5f32ca72e8d7e78868fe7c40cf1488483a49feaad06565ce272976dca68c6&xt=urn:gost94-cryptopro:bad114d3021ac70074f4cf315d78825b40141faa6502dd25f90ae6097b4fb38a&xt=urn:has160:7b0d2f95b6bf9a2beb091ddb66fa58486a8e15ec&xt=urn:gost12-256:ef405a539e4c565119537fc927e8a437c570085161fba529395bee2470be1147&xt=urn:gost12-512:237d11bc5a7f3205988675d24ae59eae6fe9b5604ca9fefdce0007b2f1f3a322ee36b6a2268e0fd8a63a4b7eee631cec159125a34bad7640febca983e148616b&xt=urn:sha224:f2c43a2d1fcff46517805cae7b2704ffc307249e779f208156d78e38&xt=urn:sha256:10aa072e2a340490550b75a3b31cc7bc2477675a86545efe10485255aae52dc4&xt=urn:sha384:5baf49ca38a7520d83e32cd34ceff2307a9ab58a968b289f4af60c3ca4652f536cd37308c4399058172923766cab7d18&xt=urn:sha512:29a41cec78761ade9d4da49c16c2b24f62a437bd4eef97948a3ae8fdb4498f64783e66000b5d53ac46dc90ffe22d4dc0a43d3d108798663a97c46138efc72b5f&xt=urn:edon-r256:05b271edb1ee478361d2b8cf2c7e2b30a98e96dc07d05c9afff5f04313ea497c&xt=urn:edon-r512:8697ed76da42f16abe913bcc3c4b73b8511dbf6117db35e9373401d03e56853a4297eaa46a9aec1c32e050ca11b1c4da33869a06f758234dfd8a6178da2cacba&xt=urn:sha3-224:0ffb43bb4c352cc2b5ee8d1386ec8949eed32403130bf8bab71d3f02&xt=urn:sha3-256:835b2f4ffad2efad5fd67b84508dbc41b4d1f977aee2a76fcc47245681b68dc3&xt=urn:sha3-384:81cb38988764b1941f4d50cacbfa0e98989128319508940558c1665f3edddb79d475495cd9962b76b2409f35066fa8d6&xt=urn:sha3-512:d50d706b9cbdab52d1564f0f89013194c60e9d158ce6bf714f35742949bfa7cfc3f3716fd8f1577c3a4755b42a30091b113aa20d15608fccffde46c62494faa6&xt=urn:crc32c:86313da6&xt=urn:snefru128:5e2348a151afe2cd50cf46c36a265c05&xt=urn:snefru256:401be5eb26ad7ba6f75dbfab9d8b66692bca8f3090eb69b75657824d8cde09e5&xt=urn:blake2s:aaf9ad51bb34f13b934decdec05989012fb2d34641d4de901bda3cd217b2e64f&xt=urn:blake2b:92cec72f95822075735249de8bb4014386ba7a71c22428fd44e7a071ed372034c2b76bdefe45824d2ab7ba8d1fbaa726d5210aa10cec7510308528495cd2386d  
$  

Instagram/Threads has been implementing very difficult to bypass controls for content. If you can't easily get it, it's probably not worth it.