I have a 2017 24” iMac with a Fusion HD (SSD & hard disk). I erased all of that. How do I restore now??

The 2017 imac was getting slower and then died. I could not mount the hard drive to do first aid. I do have a bootable external. I brought up the computer there and tried to run first aid … no good. I figured I would restore from that but would not work.

So I bought a 2021 M1 Mac. I got that all up and running.

Time to sell or destroy the 2017. But how do I erase stuff now that the drives are down. So I boot it up again with the external drive and a miracle happened and I got access to the internal drive of the 2017. I erased everything including the SSD and the Disk in the fusion drive.

For the heck of it I ran DU first aid and now all the drives look good #@$%^!@.

So I would like to restore the system back on the 2017. Then sell it at a cheap price and provide the history.

But… Since I erased everything the recovery files are gone right? I cannot get the restore to work in DU when I boot from the external. If I have that unhooked and hold down command R all I get is the internet recover. is that my only option to restore?