Please help me software brick (all data erase) my iPhone 5c in-hand
No easy workarounds if iTunes won't restore / erase an iPhone in normal mode, let alone when you have it in DFU mode. Apple Configurator might be worth a try, but it uses the same library / underlying erase code the last time I checked. Same with Xcode.

I suppose the only workaround is to disassemble it and destroy / sanitize the data by jumping some of the pins to take control of the storage. The getting it open might be easy for most skilled people - the jumping the pins would need specific technical tools and training as would getting a controller to erase systematically the data.


Physical destruction would be the alternative to software erase
repairing the phone to functionality also would be an alternative