How To Downgrade Horizon Zero Dawn

Someone made it really easy to do just Download.
https://github.com/PercentBoat4164/HZDDowngrader
Unzip it.
Ensure you have these programs available on your Linux distribution: unzip, wget, basename, dotnet, md5sum (the only one you are likely not to have is dotnet; you can install it with

snap install dotnet-sdk --classic --channel=latest/edge

Open HorizonZeroDawnDowngradeScript.sh with an edit programs like notepadqq.
And edit the top line.

To where you have your game if its in the main folder like .steam, then it has to look like this

HORIZON_ZERO_DAWN_DIRECTORY="$HOME/.steam/debian-installation/steamapps/common/Horizon Zero Dawn"

and save the file.

Now make the file execute by right click on it and properties.

Open the terminal and say CD (link to HZDDowngrader-1.1 Folder) and push enter.
now put this command into the terminal and push enter.

Sudo ./HorizonZeroDawnDowngradeScript.sh

You will be prompted for Steam username and password as well as the 2FA code two times.

Then it will do the rest for you.