No. The checkm8 exploit is a hardware vulnerability in the bootrom. Apple fixed it starting with the A12 Bionic chip (iPhone XS/XR). Gaster will never work on those devices, regardless of OS. For A12+, you need software exploits (e.g., fugu15 , kfd ), which operate at a higher level and cannot achieve true pwnedDFU mode.
If successful, the tool will confirm the device is in pwnDFU . Supported Devices Gaster targets devices with , including : iPhone : 4S through iPhone X. gaster pwndfu windows