[Bug]: NTSync not working on Proton GE and other Wine enabled version

[VinegarLove]

Describe the bug

All version of NTSync compatible version don't enable it by default, as it should be when ESYNC and FSYNC are disabled. That is, chosing "System" in the sync option.

This doesn't happen launching every Wine version from:

• Steam custom game
• Lutris
• umu-launcher
• Manually via commandline

This bug is present both in Flathub version and Native packaged version.

To Reproduce

1. Install any Wine enabled NTSync version
2. Install a custom application, possible that uses VK3D or similar to test
3. Enable MangoHud
4. Run the Application, check MangoHud and see that the WSync is neither set to ESYNC, FSYNC or NTSync.

Package

Flatpak from Flathub

Distribution

Arch Linux

Debugging Information

Official Package: false
Version: '51.21'
DE/WM: gnome
Display:
    X.org: true
    X.org (port): :0
    Wayland: true
Graphics:
    vendors:
        amd:
            vendor: amd
            envs:
                DRI_PRIME: '1'
            icd: /usr/share/vulkan/icd.d/radeon_icd.i686.json:/usr/share/vulkan/icd.d/amd_icd64.json:/usr/share/vulkan/icd.d/radeon_icd.x86_64.json
    prime:
        integrated: null
        discrete: null
Kernel:
    Type: Linux
    Version: 6.15.9-arch1-1
Disk:
    Total: 105089261568
    Free: 40416731136
RAM:
    MemTotal: 30.9GiB
    MemAvailable: 23.0GiB
Bottles_envs: null

Troubleshooting Logs

Additional context

No response

[syntheticbit]

The comment https://github.com/bottlesdevs/Bottles/issues/3905#issuecomment-3160420226 has details.

Bottles doesn't use the proton script to set the correct environment variables so at least for now you need to set WINENTSYNC=1.