apt upgrade killed my Pi

@MichaIng What’s the fastest way to get my Pi 4 working again? I don’t have a display unfortunately but running

apt update


apt upgrade

today killed my device. It won’t appear on my network now over Ethernet.

Something happened during the upgrade process and the ssh connection timed out and now it won’t appear on the network at all.

I’ve a backup from a few days ago that I would like to restore. How do I do that without a screen and without being able to ssh into the device so I don’t have to go through all the pain of setting up the device again and making all of the directories etc.

If I can’t restore the backup. Is it possible to just overwrite the SD card image without ruining the settings I made on the distro?