Recover data from corrupted APFS external volume

Here's how to do this:

1. Create bootable USB Stick for Ubuntu:

   If you have a Mac that has a T2 chip, you must first allow the computer to start from other removable media.

2. Once you get Ubuntu running, go to "software & updates" and select everything or you will not get the required community-maintained packages when doing "sudo apt update"

3. Now we install something called APFS-fuse, which allows Ubuntu to mount and read drives that have been formatted with Apple's APFS file system

4. run sudo apt remove zsys or you will get an error later

5. run (source: https://linuxnewbieguide.org/how-to-mount-macos-apfs-disk-volumes-in-linux/)

   sudo apt install libicu-dev bzip2 cmake libz-dev libbz2-dev fuse3 libfuse3-3 libfuse3-dev clang git libattr1-dev

   git clone https://github.com/sgan81/apfs-fuse.git

   cd apfs-fuse

   git submodule init

   git submodule update

   mkdir build

   cd build

   cmake ..

   make

   sudo cp apfs-* /usr/local/bin

6. Run sudo fdisk -l and find the identifier of your disk. Say its "sdb1"

7. sudo mkdir -p /media/$(stat -f %Su)/macos

8. Mount the disk:

   sudo apfs-fuse -o allow_other /dev/sdb1 /media/ubuntu/macos

   it will appear in the file viewer and you can see your files. Because you need Ubuntu to see files stored in a filesystem made by Apple...