I program in C professionally. It's a good language to learn how processors actually work. It's on the embedded side, where there are other options but either

I program in C professionally. It's a good language to learn how processors actually work. It's on the embedded side, where there are other options but either they're not mature (Rust) or were never really taken up (Ada). Embedded C it's just you and the hardware. It's a good way to learn about what's actually going on. Anything, like an Arduino or Arm cortex is great. Small warning about ESP32 boards - some are based on the Extensa cores, which means you need to use their compilers. Others are based on Risc V - do your research.