Use a USBtinyISP as a programmer or re-purpose an Arduino board you might already have to upload anything even to mainboards that do not come with a bootloader installed.
Hey @Thomas Sanladerer - I really need your help!!! After getting the USBTinyISP, I’ve followed your steps with no BOOTLOADER and here now my Ender 3 doesn’t boot up and remains on the blue screen with nothing. It is now refusing to communicate.
If you can’t get the USBtinyISP to work, try using an Arduino as ISP according to Arduino’s manual: https://www.arduino.cc/en/tutorial/arduinoISP
Sounds good. Thank you for the direction.