Magic-1 is a completely homebuilt minicomputer.  It doesn't use an off-the-shelf microprocessor, but instead has a custom CPU made out of 74 Series TTL chips.  Altogether there are more than 200 chips in Magic-1 connected together with thousands of individually wrapped wires.  And, it works.  Not only the hardware, but a full software stack. There's a ANSI C cross-compiler for Magic-1 (retargeted LCC), a fully multi-user, multi-tasking port of the Minix 2 operating system. a TCP/IP stack and hundreds of programs.

It uses https://emacs.love/weblorg/doc/index.html
Found on https://sachachua.com/blog/2021/11/2021-11-22-emacs-news/ via https://www.lucacambiaghi.com/posts/ipad-main-computer.html

See the output of several compilers in your web browser.
In addition to C++, it now supports Go, Rust and D.

GNU Mes brings a Reduced Binary Seed bootstrap to GuixSD and potentially to any other interested GNU/Linux distribution, and aims to help create a full source bootstrap as part of the bootstrappable builds effort.

It consists of a mutual self-hosting Scheme interpreter written in ~5,000 LOC of simple C and a Nyacc-based C compiler written in Scheme. This mes.c is being simplified to be transpiled by M2-Planet.
https://github.com/oriansj/M2-Planet

The Scheme interpreter (mes.c) has a Garbage Collector, a library of loadable Scheme modules– notably Dominique Boucher's LALR, Pre-R6RS portable syntax-case with R7RS ellipsis, Matt Wette's Nyacc –and test suite just barely enough to support a simple REPL and simple C-compiler: MesCC.
https://github.com/oriansj/mescc-tools

Mes+MesCC can compile an only lightly patched TinyCC that is self-hosting. Using this tcc and the Mes C library we now have a Reduced Binary Seed bootstrap for the gnutools triplet: glibc-2.2.5, binutils-2.20.1, gcc-2.95.3. This is enough to bootstrap GuixSD for i686-linux and x8664-linux.

Mes is inspired by The Maxwell Equations of Software: LISP-1.5 – John McCarthy page 13, GNU Guix's source/binary packaging transparency and Jeremiah Orians's stage0 ~500 byte self-hosting hex assembler.

GNU Mes is free software, it is distributed under the terms of the GNU General Public Licence version 3 or later. See the file COPYING.

LNG is an operating system primarly for the good old Commodore64 home-computer. There also is a native version for the successor Commodore128. Ports to other 6502/6510 driven 8Bit Computers are possible but not yet started. LUnix started in 1993 and reached the internet in 1994. In 1997 LUnix0.1 was rewritten from scratch, the result is LNG.

Abstract.
ElsieFour (LC4) is a low-tech cipher that can be computed by hand;
but unlike many historical ciphers, LC4 is designed to be hard to break. LC4 is intended for encrypted communication between humans only, and therefore it encrypts and decrypts plaintexts and ciphertexts consisting only of the English letters A through Z plus a few other characters. LC4 uses a nonce in addition to the secret key, and requires that different messages use unique nonces. LC4 performs authenticated encryption, and optional header data can be included in the authentication. This paper defines the LC4 encryption and decryption algorithms, analyzes LC4’s security, and describes a simple appliance for computing LC4 by hand.

An extended version called LS47 can be found on https://github.com/exaexa/ls47, which includes a 3D-printable model of the tiles.

The Deep Sweep is an aerospace probe scanning the otherwise out-of-reach signal space between land and stratosphere, with special interest placed in UAV/drone to satellite communication.

A port of BSD2.11 to a MIPS-based microcontroller with 128 kiB RAM.