well there is still an option to flash an unrooted kernel that is compatible and then try to root it, but dont know if it would remowe that yellow death from start screen caus i newer rly had that problem. Best would be to reset your download mode counter with an USB jig if all other options fail. Then you wont have any yelow triangle there. You may have to plug the jig in and start like this download mode a few times if it dont work on first
its also easy to make one home, just need an mikro usb conector + rezistor 301K ohm.