As for GitHub repositories from 2021 related to EX4 to MQ4 decompilation, I was able to find a few relevant repositories:
Modern EX4 files (compiled with MetaTrader 4 or higher) use advanced byte-code protection. This makes a clean "one-click" decompilation back to readable MQ4 source code nearly impossible with public tools. Key GitHub Repositories and Tools ex4 to mq4 decompiler github 2021
If you are looking for open-source projects to study the logic, use these specific search terms on GitHub: mql4-decompiler ex4-to-mq4-converter mql-reconstructor 3. Pure Logic Extraction As for GitHub repositories from 2021 related to