The bootloader is read-only, the firmware it boots is updateable. The bootloader allows you to update the device with new firmware. MCU are different than comp

The bootloader is read-only, the firmware it boots is updateable. The bootloader allows you to update the device with new firmware. MCU are different than computers. And since you can't overwrite the bootloader, you can't brick the MCU. You can always just reset it. fwiw; I've never bricked an MCU buy flashing something weird onto it. The hobbyist MCUs sold are typically quite easy to re-flash with new firmware.