Hello,
If your device has a bootloader with v1.x.x, bootloader update is not possible and will permenantly damage the device. In thay case, I'd recommend looking into the newer devices like RUT956, RUT951, or RUT901 which will be a perfect replacement.
If you device is on a newer bootloader, could you clarify the reason why you'd like to update it?
Best regards,
DaumantasG