Your system information

• Steam client version (build number or date):
• Distribution (e.g. Ubuntu):
• Opted into Steam client beta?: [Yes/No]
• Have you checked for system updates?: [Yes/No]

1. Built: Apr 12 2021, at 18:51:43
2. Slackware64-Current
3. No
4. Yes

Please describe your issue in as much detail as possible:

Describe what you expected should happen and what did happen. Please link any large code pastes as a Github Gist

I'm using Proton 6.3-2. When I press "PLAY," I have two options: "Play Murasaki Tsurugi" and "Launch Configuration Tool." The Configuration Tool works fine as far as I can tell. The game starts and runs according to the Steam client but no game window appears. I have to press "STOP" in the Steam client to get the game to stop running.

Here is the PROTON_LOG=1 file. https://gist.github.com/EpicureanGit/f5b7deb5b9bd56296ce610dbd37fae90#file-gistfile1-txt

Steps for reproducing this issue:

Press "PLAY" in Steam client, select "Play Murasaki Tsurugi," and select "PLAY" in the popup menu called "Murasaki Tsurugi - Steam."