### System Information
*   **OS:** CachyOS (Arch Linux based)
*   **KDE Plasma Version:** 6.x (Wayland)
*   **KDE Frameworks Version:** 6.x
*   **Qt Version:** 6.x
*   **Graphics Hardware:** NVIDIA GeForce RTX 5070 Ti (GB203 architecture)
*   **Driver Version:** 610.43.02 (Proprietary)
*   **Display Manager:** SDDM (configured to run on Wayland with `kwin_wayland`)

### Description
When logging in from SDDM (which is configured to run on Wayland using `kwin_wayland`) to a user Plasma Wayland session, the screen goes black and the monitor loses signal. 

Investigation of `journalctl` shows that during the session transition, the SDDM greeter compositor exits, but the incoming user `kwin_wayland` session fails to commit frames to the DRM device due to a permission error:
```text
sddm-helper-start-wayland[960]: "kwin_wayland_drm: atomic commit failed: 权限不够\n"
sddm-helper-start-wayland[960]: Stopping... "kwin_wayland"
```

The system remains running in the background (no signal to display). 

**Workaround:** 
Pressing `Ctrl + Alt + F3` to switch to TTY3, and then `Ctrl + Alt + F2` to switch back to the GUI session on TTY2 immediately restores the signal and displays the desktop. This suggests switching VTs forces a reset or release of the DRM Master lock, allowing the user's `kwin_wayland` to successfully gain control.

Changing SDDM's display server back to `x11` completely bypasses this issue, suggesting a race condition/deadlock in DRM Master transfer between the SDDM Wayland greeter and the user's Wayland compositor on NVIDIA.

### Steps to Reproduce
1. Configure SDDM to run on Wayland (using `kwin_wayland` as the compositor).
2. Boot the system and reach the login screen.
3. Enter the password and press Enter.
4. Observe the screen going black/losing signal.
5. Switch to TTY3 and back to TTY2 to restore the screen.