No tool required. Just core Linux utilities.
If your goal is rooting, stop looking for ramdisk tools. (by topjohnwu) is the modern solution. It patches the boot image directly on your device or via the Magisk app. pak ramdisk tool free
The Android ecosystem is shifting toward init_boot partitions (Pixel 6 and newer) and dynamic partitions. As of late 2024, the developers of are working on a version 3.0 that supports Generic Kernel Image (GKI) 2.0 structures. The free version will continue to support legacy devices (Android 5.0 to 13), while advanced GKI support may eventually move to a "Pro" tier. No tool required