On the question what are use cases for a Gemini server:

Gemini is kinda a modernized version to the old Gopher protocol. Its purpose is to share hyper-linked text documents and files over a network - in the simplest way possible. It uses a simple markup language to create text documents with links, headings etc.

Here is a FAQ

Main differences with similar technologies are:

• It is much, much easier to write hyper-linked documents than in HTML

• a server is much much smaller and easier to set up than a web server serving HTML. It can easily and securely run on a small Raspberry Pi without special knowledge on server security.

• in difference to gopher, it supports modern things like MIME and Unicode

• There are clients for every platform including Android and iOS

• also, there are Web gateways which allow to view stuff in a normal web browser

• unlike Wikis, it is only concerned about distributing content, not modifying files. This means that the way to store and modify content can be matched to the use case: Write access to content can be via an NFS or Samba server, or via an SFTP client like WinSCP or Emacs.

• Unlike HTML2, it does not support advertising, tracking, spying to users, and so on.

• the above two points mean that it does not need user authentication

• the protocol is text-centric and allows for distraction-free reading, which makes it ideal for self-hosted blogs, small projects or associations, or microblogs.

Practically, for example, I use it to share vacation photos with family.

Two more use cases that come first to my mind:

• When I did my masters thesis, our lab with about 40 people had a HTTP page hosted on a file server that listed tools, data resources, software, and contact persons. That would be easier to do with Gemini because the markup is simpler. Also, today it would not be feasible to give every student write access to a Apache web server's content because of the complexity of web servers, and the resulting security implications.

• One time at work, we had a situation with a file server with many dozens of folders, and hundreds of documents. And because all the stuff had been growing kinda organically over many years, specific information was hard to find. A gemini server would have made it easy to organize and browse the content as collaboratively edited hypertext which serves as an index.