Winter is coming and Collapse OS aims to soften the blow. It is a z80 kernel and a collection of programs, tools and documentation that allows you to assemble an OS that can:https://collapseos.org/
Run on minimal and improvised machines.
Interface through improvised means (serial, keyboard, display).
Edit text files.
Compile assembler source files for a wide range of MCUs and CPUs.
Read and write from a wide range of storage devices.