I have a laptop with a primary HDD containing Windows and an old installation of Backtrack 5. I have a second SSD in a hot swap bay. I started to install KDE Neon on the SSD in the secondary bay when things went wrong.

I selected the correct disk and then selected the radio button to set up Guided LVM with encryption. Selecting the radio button changed the drive selection back to the default. (Why I have no idea.) I noticed the change just after pressing the next button. I immediately powered off the machine to discover that it had already deleted the partitions off of my primary drive without confirmation. (Gparted shows the empty unformatted Linux partitions taking up the entire space of the drive.)

The paritition table was deleted, but I think the data should still be intact since I did not proceed to the format. How can I go about recovering the partitions? I attempted to use TestDisk but it can't get past the fact that it sees the new, valid MBR.

I was dual-booting Windows 10 with EasyBCD but it was an upgrade from Windows 7. I believe I was using a legacy MBR and not a GPT but I can't be completely sure.

You may want to give testdisk a try. I am in no way affiliated with the project but thought it might be of help.

https://www.cgsecurity.org/wiki/TestDisk

I have run Testdisk. When you first analyse, it only see the two new partitions. One ext2, and one LUKS. After a deep scan it shows dozens of partitions which is not correct. I've identified the two partitions I believe I need based on size, but the file list appears encrypted. Neither of the volumes was encrypted so I'm not sure Testdisk is finding the right partition boundaries.