Follow some of the other links. The self-write to flash was developed for other processors first. I was trying to find the bootloader that had it originally, this was the best I could find.
There have been lots of add-ins to the IDE to support similar 8-bit AVR microcontrollers. Read the directions, add the various MiniCore, MegaCore, MightyCore, etc. and use other uCs the same as you would an Uno.