Attach Old Disk to new MyCloudHome

Unfortunately no, at least not with the old 7.16 firmware and no new USB functionality has been documented since to suggest that this has changed. Your question is basically asking if the MCH OS will mount and decrypt the “shucked” MCH HDD through USB as a ‘private user space’ partition and the answer is no, it will not mount partition 24 as such, in fact a MCH won’t mount partition 24 at all through USB.

WDC does not support user DYI data recovery so they will not answer these types of questions.

There are good descriptions of how to use a recovery script in the thread below, unfortunately very few home users would know how to go about using it or they may have done too much damage to their data disk by resetting it or writing to it with other recovery software. There have been in the past a lot of spam posts describing how their $699 software is going to recover user data for unwitting MCH home users, but all the Linux data recovery software are free to download and use as described by some others who were not trying to con people. A free Linux software that works is rescuezilla as described below and is totally free.