All sorts of problems getting this game started.

Ultimately, the trick seems to have been;

Set the lauch options to:

gamescope -H 2160 --force-grab-cursor -F fsr -f -- ~/.local/share/Steam/steamapps/common/SNOWBREAK/fix.sh %command%

Don't forget to update -H to your intended resolution, and to remove --fsr if you're not using an applicable AMD card.

Also, you'll need to create a file called fix.sh (you can see where I put it in the command above) with the following content;

#!/bin/bash

# Iterate through all arguments
for arg in "$@"; do
# Remove the substring "-steamapp" from each argument
modified_arg="${arg//-steamapp/}"
# Add the modified argument to a new array
modified_args+=("$modified_arg")
done

# Execute the command with the modified arguments
exec "${modified_args[@]}"

Don't forget to mark it as executable - now the game should launch.

Now, I couldn't create an account (I ended up doing that in windows) but once you have one don't forget to tick the very subtle "i agree" tickbox underneath the login button.