> Some recent examples of such low-level work I can think of, are: Linux kernel development, sanitizers and static analysis in GCC and Clang, new languages and

> Some recent examples of such low-level work I can think of, are: Linux kernel development, sanitizers and static analysis in GCC and Clang, new languages and their compilers and tools (Rust, Go, WebAssembly, etc), regular improvements in web browser engines, databases features. All that you have listed are available for contributions from beginners. Choose the field you like and start lurking on their mailing lists; download the source code, try to understand it and ask questions (let developers on the mailing list know that you are a beginner and want to contribute, and ask what is the best approach to get to speed with the codebase)