Another option would be to desolder the emmc chip from the phone, put it in an adapter so you can connect it to the PC.
You would still need some software to handle the partition table on the emmc which has an offset. Then you should be able to access the partitions. You may also need to add support for the filesystems.
This will most likely void your "warranty".
But is probably the only way to access the partitions on an android device.