You could try booting from a USB installer. Use DU to completely erase the internal drive (normally a very bad thing to do, and forcing the use of Configurator) but in your case it might prepare the internal drive such that Configurator could work.
At this stage I don't think you have anything to lose by trying this.
EDIT you would have to create the USB installer on another Mac if you dont have one, but you can do this on an Intel Mac.
Thanks for the suggestion! I cannot boot into recovery so I can’t choose to boot from an external drive. I do have a USB installer so tried booting with it inserted but no luck.
Attempting to boot from the other recovery system with a double press and hold of the power button doesn’t work either.