IPFS seems like a perfect fit for this and some of the scihub torrents are already in IPFS, but it's not an anonymous network.
IPFS via the DHT tells the network of your whole network topology, including internal address you may have, and VPN endpoints too. It's all public by design as they don't want to associate IPFS with piracy per one of their developers.
Can files be taken down off ipfs? There was a fairy widely circulated link that had all the IEC and ANSI standards on there that has since been taken down.
You could use libp2p's DHT over Tor (I did a poc of this long ago, and the situation's only improved). Combined with other libp2p/IPFS components, you can essentially have a private IPFS over onion services (not to be confused with accessing the existing IPFS network via Tor exit nodes).
some torrent files are archived there, but i don't think scihub is serving the pdfs from IPFS, they likely use private storage network.
I believe libgen.fun which is a new (official) libgen mirror is running fully on ipfs, and it serves some scientific papers, but I wasn't able to search by DOI or title there, looks like it redirects to scihub, also there is no index of the papers on IPFS.
Edit: this doc talks about scihub+ipfs (it was created by the leader of Scihub rescue effort on Reddit, /u/shrine): https://freeread.org/ipfs/
IPFS via the DHT tells the network of your whole network topology, including internal address you may have, and VPN endpoints too. It's all public by design as they don't want to associate IPFS with piracy per one of their developers.
this thread has some discussions on the alternatives https://www.reddit.com/r/DataHoarder/comments/nc27fv/rescue_...