Most people use C, some use C++ or assembler; other languages are also used, but are much less common on MCUs; if it's a hobby project you can even use somethin

Most people use C, some use C++ or assembler; other languages are also used, but are much less common on MCUs; if it's a hobby project you can even use something like CircuitPython, which works well e.g. on the Raspberry Pi Pico.