Troubleshooting steps already taken:
1. Switched from newest proton to latest numbered version (10-25).
2. Enabled "Use Steam Runtime" in game options.
3. Tried to install another gog game (Jade Empire) and it also cannot launch.
4. Ran the flatpak update/install command and received the same error.
See attached log file. Note that I've edited the filepaths to remove my username.
Thank you in advance!