@crowgirl
Here's the content from your Reddit post, for convenience:

Linux partition crisis, I need data recovery, help!
I was using Kubuntu 24.04 without problems for well over a year.

Then some update messed with my NVIDIA drivers and I couldn't launch any of my Steam Linux games, Vulkan errors.

After messing around with various NVIDIA driver packages, I lost my ability to boot into my operating system.

I am now running Kubuntu 20.04 from a LiveCD.

Help me!

I tried all kinds of things with truecrypt, veracrypt, cryptsetup. No success.

LiveCD OS does see the Kubuntu 24.04 partition. It's /dev/nvme1n1p2, mounted on /media/kubuntu/kubuntu_2404

I know the password to that partition. But it doesn't seem to use LUKS encryption.

Cryptsetup and LuksOpen doesn't work because I get "/media/kubuntu/kubuntu_2404 is not compatible" and "/dev/nvme1n1p2 is not compatible"

Trying to install from LiveCD is a scary risk because when I tried the installer, there was no indication that it would preserve my documents in the old /dev/nvme1n1p2 24.04 partition.

So I'm not trying that.

A book that I owe Kickstarter backers is on that partition.

I know the password for whatever encryption is on there!

And it is ext4.

But it doesn't seem to be LUKS encryption.

And I can't figure out what it used for encryption. Or how to use the OS sudo password I was using to log into 24.04 to decrypt it so I can recover it.

Help!

I am in a crisis. 😭😭😭