Old Windows 10 BitLocker SSD does not boot after cloning from it with gddrescue in Linux

I have a problem booting my dad's HP computer after copying data from its SSD to a new SSD. Neither the old, nor the new one boots. Please help, I am afraid I may have lost all my data. I need the computer to boot again normally.

TDLR: copied data using ddrescue from old to new SSD, now both SSDs won't boot. It's a Windows 10 drive with BitLocker.

Error is blue screen with 0xc000000e error.

HP computer: HP ProDesk 400 G4 Small Form Factor

Here is what I did:

1. I have a 256 GB SSD and bought a 1TB SSD.
2. I created an Ubuntu USB disk and booted the computer with it to copy all the data from the old to the new SSD.
3. I used an older Sata-to-USB-2.0 adapter to connect the new drive.
4. I used the following command: ddrescue -f -n --ask /dev/<old> /dev/<new> /path/to/log
5. It took way too long, so I hit Ctrl+C
6. I connected both drives using SATA to a different, newer computer and performed the same command in 10 minutes.

Between steps 5 and 6 I noticed fdisk complaining about a missing "GPT backup at end of drive", which I assumed to have been from the halfway-copied-into-SSD. I may have looked wrong and it may have been the old SSD, although the problem wasn't there before any of the copying took place.

Result: The HP computer will not boot using any of the two drives. Important to note: I only realized my dad uses BitLocker after I copied the data. Clearly this is related, but I do not know how to fix the problem.

Of course I feel like an idiot, I was completely convinced simply copying data off a drive bit-by-bit could do no harm. I am a programmer so I should have known better than NOT to make a backup, but I am convinced I used the ddrescue command correctly.

Things I've tried:

1. disable/enable CSM
2. disable/enable secure boot
3. change boot order back to the original (not sure what the original is now anymore...).
4. Create USB windows installation media to somehow get a repair screen to show, but no luck.

You need to get the "recovery key". Usually it's was stored in a file or with your Windows account - if you have one. In cooperate settings the domain controller might be setup to store it as well.

Decrypt the volume on the new SSD, run bootrec /fixmbr and format the EFI partition. That should make the new SSD boot again.