_private_data.tgz is a local file where what is local copies are stored. It doesn't need to be sent anywhere... in fact, it often has a copy of what is received, as well as what is collected locally.
There will be a TGZ file created with the name of the disk and 4 hexadecimal characters created, assuming you've enabled it. It will be mentioned in the data displayed when the disk is opened. THAT is the file you forward to svg@makemkv.com to have analysed, and from which the key is generated.
Ambulance UHD Disc
Re: Ambulance UHD Disc
MakeMKV Frequently Asked Questions
FAQ about BETA and PERMANENT keys.
How to aid in finding the answer to your problem: Activating Debug Logging
FAQ about BETA and PERMANENT keys.
How to aid in finding the answer to your problem: Activating Debug Logging