Initially, I couldn't find the correct combination as I had used the Prusa MMU combination, which failed every time. Only after looking at the prusa3d forum did I realise that the settings for the Rambo should be used. Hopefully, this change could make it clearer to MK3 users without a MMU for which combination to use.
Please merge this. I hit on this exact issue and can confirm that ATmega2560 set to wiring for Prusa i3 MK3S and i3 MK3S+ is the correct setting. This is very helpful.
Initially, I couldn't find the correct combination as I had used the Prusa MMU combination, which failed every time. Only after looking at the prusa3d forum did I realise that the settings for the Rambo should be used. Hopefully, this change could make it clearer to MK3 users without a MMU for which combination to use.