Lagrange is a graphical client in C/SDL.
I really love the rendering of Gemini pages in this client. I’m not sure this will be my Gemini client on the long term as I’d prefer something with a better integration in KDE. The developper is really active and fixes bugs as soon as you report them. This client supports gemfeeds, has bookmarks, history, it’s quite feature complete. It chooses a random emoji as favicon for each domain, which is quite a nice idea too.
Kristall is a graphical cient in Qt. It would fit better in my KDE/Plasma desktop, but it’s quite limited compared to Lagrange. It is also able to browse other protocols, including the web, but it renders only a subset of HTML, in a similar way as Gemini pages. It works well for some website, and not at all for some others.
Ariane is an Android Gemini client. It’s quite simple, and a bit unstable, but it’s the only one I found for Android which is easy to install.
I did not look into servers that much yet, as I am using my own server I implemented in PHP.