>There's nothing really like it anymore - you can't have anonymous sftp.
Strictly speaking there's nothing stopping someone from writing an anonymous sftp server that lets anyone log in as a 'guest' user or similar - it's just that nobody has (as far as I'm aware).
"Unauthenticated SSH" is basically what the git:// protocol is. I wonder if you could use git-daemon(1) to serve things other than git repos? Or you could just convert whatever you want to serve into a git repo, I guess.
You could, but since git isn't designed for handling large binary files the performance will be poor. That's why there are large file support plugins like (the aptly named) Git LFS[0] and git-annex[1].
IPFS requires a stateful thick client with a bunch of index data, no? Would it be efficient to, say, build a Debian installer CD that goes out and downloads packages from an IPFS mirror? Because that's the kind of use-case anonymous FTP is for.
Many many years ago I was on the team that managed the compute cluster for the CMS detector at the LHC (Fermilab Tier-1).
When we would perform a rolling reinstall of the entire worker cluster (~5500 1U pizza box servers), we would use a custom installer that would utilize Bittorrent to retrieve the necessary RPMs (Scientific Linux) instead of HTTP; the more workers reinstalling at once, the faster each worker would reinstall (I hand wave away the complexities of job management for this discussion).
I'm not super familiar with IPFS (I've only played with it a bit to see if I could use it to backup the Internet Archive in a distributed manner), but I'm fairly confident based on my limited trials that yes, you could build a Debian installer CD to fetch the required packages from an IPFS mirror. No need to even have the file index locally. You simply need a known source of the file index to retrieve, and the ability to retrieve it securely.
You have to be really careful though because the default is to give users shell access. If you think you can limit that by forcing users to run some command you'll run into trouble because the user can specify environment variables.
The user also by default gets allowed to set up tunneling which would allow anonymous users to use your network address.
Strictly speaking there's nothing stopping someone from writing an anonymous sftp server that lets anyone log in as a 'guest' user or similar - it's just that nobody has (as far as I'm aware).