It's pretty trivial to do so on Arduino though.

  void setup() {
    pinMode(LED_BUILTIN, OUTPUT);
  }
  
  void loop() {
    digitalWrite(LED_BUILTIN, HIGH);  
    delay(1000);                     
    digitalWrite(LED_BUILTIN, LOW);   
    delay(1000);                      
  }

With micropython or some of the js based frameworks for microcontrollers, it's really not that new/different.Especially with ESP32/Pi Pico W/their clones...

In fact it's a lot more straight forward to not have to deal with Network Manager config files or systemd unit files or read only rootfs headaches of Linux world.

asking as a casual non-poweruser... how does one do that on linux exactly?

good news, now you can use all that dram you can't afford to vibe code an arduino program. Think of the savings and the learnings!