Yahia:
Hello,I need to use the watchdog timer in my code on the Nano and I know that the bootloader that is on the Nano is not compatible with it. I need some advice on which bootloader to go with that will support the watchdog timer as well as the normal functionality from the original bootloader.
The easiest way is to just install the standard Uno bootloader onto your Nano. It will run just fine and have the WDT fix, plus take up less space and upload at a faster baudrate. The only change you will have to live with is that once you burn the Uno bootloader to your nano, you thereafter must always select the Uno board in the IDE when uploading new sketches, not select the Nano board like you presently do.
Also, I want to burn the new bootloader with an Uno. Is this safely doable?
Yes, that is perfectly safe and doable.
LeftyCheers
Yahia