Data recovery? After HUGH rookie mistake

This mistake is so big I am very embarassed to discuss but here goes:

Installed Alma Linux 8.8 on my HP desktop, I also have an external disk for data backup. All data was transferred to this install.
Installed Cinnamon had had some issues with screensaver.
Went down a huge rabbit hole of trying to install nvidia drivers…and used nvidia-xconfig --mode to try and fix the resulting bad screen resolution. This went nowhere and was NOT a good idea.
Decided to reinstall Alma and start again.
here’s the HUGE mistake
I left the external backup drive plugged in and accidentally installed the fresh install on my backup drive, overwriting my data!
Now if I try to boot the first install on the desktop hard drive, it fails
It hangs/stalls on “started system logging service”
If I add a “1” to the end of the linux line in grub, I get "kernel panic not syncing VFS, unable to mount root fs on unknown-block(0,0)

My question is:
Should I try and fix the original broken install (my only source of my backup data, if it’s still on disk) OR should I try a data recovery service on the desktop drive.

Is there a way to see if my data is lost?

From what you’ve described this is what I’d do:

  1. Disconnect the external disk and leave it alone.
  2. Using another machine download the live media version onto a spare external drive.
  3. Boot the external disk.
  4. Mount the internal disk READ ONLY and copy the data to the external hard disk.
  5. Make a backup elsewhere.

If that worked satisfactorily (and I’m assuming that your data on the internal disk is OK) then you should have:

  • The original backup disk - probably useless but isolated for now as the last resort.
  • A live disk with the valuable data on it.
  • Another backup.
  • The internal disk.

Now redo the installation and get it working then install the data but keep the two disks containing data until at least one satisfactory backup has been done.

You’ll need to beg/borrow/steal/purchase a couple of disks, but that will be a heck of a lot cheaper than paying a data recovery service who may not be successful. That is the last resort.

Thank you for the advice…I wIll check back in with results after buying a new HD

Followed your advice to the letter and have recovered ALL data successfully…

Thank you very much!