do you know how to pack/unpack ramdisk.img and kernel to boot.img ? use magisk manager to patch boot.img .
you need these binary.
$ file /system/xbin/mkbootimg
/system/xbin/mkbootimg: ELF 32-bit LSB executable, Intel 80386, version 1 (GNU/Linux), statically linked, for GNU/Linux 3.2.0, BuildID[sha1]=23318c230c92cb349a53a31ef1154b2db94df7f4, stripped
$ file /system/xbin/unpackbootimg
/system/xbin/unpackbootimg: ELF 32-bit LSB executable, Intel 80386, version 1 (GNU/Linux), statically linked, for GNU/Linux 3.2.0, BuildID[sha1]=70ccad8ca0a724143c44b1b7401f2690125ce863, stripped
$ file /system/xbin/abootimg
/system/xbin/abootimg: ELF 32-bit LSB executable, Intel 80386, version 1 (GNU/Linux), statically linked, for GNU/Linux 3.2.0, BuildID[sha1]=e9fecb60a2fd155176fbda0e78f1a4a582b49761, stripped
$