TempleOS

Open source alternative Operating System created by the (in-)famous Terry A. Davis. I have not tested it, I just followed it out of curiosity and the drama around the creator which is most likely the main reason others know about it as well. After his death the website and operating system is maintained by the community, whoever that is. It is more a meme community than something that people really use, since due to his mental illness the operating system has limited use in real life, it is probably more something for curious people that want to learn about programming.