Kevin Bates’ Arduboy

May be considered as the “ARDUBOY Inc. Arduboy” nowadays, rather than simply “Kevin Bates'” Arduboy. A game console counting more as a “tinker” project, the Arduboy is a sort of “DIY” game console based off the Arduino hardware. Seemingly releasing in 2014 as a “Tetris business card”, the Arduboy does not really fit into the realm of either “emulation handhelds” or “conventional” handhelds, as it cannot really emulate anything, and it doesn't feature any sort of commercial games. Despite this, it can still reasonably be considered closer to the 2nd, warranting it's inclusion here in Video Game Consoles (Portable). Specifications-wise, it runs off one of the Arduino boards…

https://www.arduboy.com/

Operating Systems (Arduino-based)

AOS

But in form of a command shell this software controls the hardware of the Arduboy

A surprisingly fully featured little OS for this device. Features a terminal, a watch, calculator, full control over the system in all available outputs, and more. While it does lack multi-user function as for multitasking, it still gives a strong impression of “operating”.

https://github.com/zooxo/aos

https://www.youtube.com/watch?v=dVvj3j-pYlQ

https://community.arduboy.com/t/aos-arduboy-operating-system/6717

Ardutosh

Notes text editor allows you to save text to the EEPROM

A simple but also functional clone of the Classic Mac OS desktop environment. Features a terminal, an EEPROM monitor, a remote keyboard/mouse function, and more.

https://github.com/jhhoward/Ardutosh

https://community.arduboy.com/t/ardutosh-classic-macintosh-style-desktop-environment/8298

Pocket PDA

It includes seven Apps for the moment, but can barely hold more

Self-describes as a Toy OS, but is capable of doing a few simple PDA-esque tasks, as it’s in the name. The GitHub repository appears to have been taken down, hence the archive link.

https://community.arduboy.com/t/pocket-pda-v0-8-0-a-toy-os/2869

https://web.archive.org/web/20180613071013/https://github.com/pocket-arduino/pocket_pda