After I set up Flutter and got flutter doctor running, I plugged in my Android phone. Neither flutter doctor or VS Code could detect it!
I already turned on Developer Options and USB debugging “File sharing”.
Developer Options > Select USB Configuration > Change it from “File Transfer” (default option) to Charging”
The phone will ask if you want to always allow USB debugging from this device.
Say yes.
After that, VS Code was able to detect my Android phone, and I was able to run my app on it!