did you back up your nand while it was still connected to your nnid?
plaitect did has a guide for that section in his wiki https://github.com/Plailect/Guide/wiki/DSiWare-Downgrade
I've owned both iPhone and Androids over the years. Both are just as good, other than Apples higher price. I'm currently on Android, Samsung S21 I think, and very happy with it.