How do I flash back to iode' or Lunar OS?

I got root in Lunar OS! The fastboot command in that thread I found was wrong. The one George posted has the right fastboot command. U need to have flash in there. I unlocked the bootloader first which is described here:

i used Magisk and it wanted to finish up things and reboot. I checked with the root checker app and see this:

Now I need an app that can write my IMEI numbers back!