resources
Here are some things that have helped me out recently.
Java
The University of Helsinki's Massive Open Online Course (MOOC), specifically their Java Programming course.
C++
The Learn C++ website.
This resource is great because it explains C++ concepts in a beginner-friendly way while still offering valuable insights for those with experience in higher-level languages like JavaScript or Python, especially about how languages work and compile down.
PlatformIO is an open-source ecosystem for embedded software development. In their own words: "Your Gateway to Embedded Software Development Excellence."