Firmware recovery solutions

Hello

After recent experiences with faulty FW update, I am looking for some tips for recovery.

After sale service works great, but I wonder if there is a method to recover instalation files by ourselves.

In case of Windows CE it was simple by replacing the file system.

Do you know any similar method in modern units with Linux system?

I think it should be possible as well, but probably need to join the programming unit directly to the mainboard of modern unit, after unscrewing the case...

I would welcome any possible solutions without need to wait several weeks to repair it in Spain...

Regards

Marek