To be able to mount a macOS filesystem you either need to install kernel modules for HFS or for APFS depending on how recent the macOS version is.
If it’s HFS (the older filesystem) you only need to “sudo apt install hfsprogs”.
If it’s APFS (the newer filesystem) things get much more complicated. Attemts at reading the APFS filesystem has been attempted and there’s a kernel module you can compile and run for read-only access but as far as I know nothing for write access.
But I assume that it should be possible to boot a disk without mounting it, I think you have better chances with doing that if it’s APFS.