Dear Maintainer,


When using COSMIC Dekstop on Debian 13, I found that all apps crash
after compiling a version after the following:

https://github.com/pop-os/cosmic-
comp/commit/091583ac84abac02967ae358cf9570ddfef63b31 (backend: Support
wl-dmabuf v6)

Debugging showed that the gtk-4 version included in Debian 13 (4.18.6)
announced support for versions higher than 5 while it does not seem to
implement what is needed for proper v6 support.

patching gtk4 to only announce v5 support fixes the problem.

A patch is attached.

Dear Maintainer,
I can reproduce what appears to be the same issue on Debian 13 Trixie with the Niri Wayland compositor and libgtk-4-1 version 4.18.6+ds-2.

Both Loupe and Nautilus consistently crash with SIGSEGV during GTK4 Wayland display initialization.

I tested the following workarounds:

- GSK_RENDERER=gl: still crashes
- GSK_RENDERER=cairo: still crashes
- GTK_THEME=Adwaita: still crashes
- GDK_BACKEND=x11: both applications work correctly through XWayland
The Loupe coredump shows the following stack frames:

```
#0  libgtk-4.so.1 + 0x47d730
#4  libwayland-client.so.0
#6  wl_display_dispatch_queue_pending
#8  gdk_display_manager_open_display
#9  gtk_init_check
#10 gtk_init
```

This appears consistent with the Wayland dmabuf v6 issue described in this bug, although I have not independently verified the root cause.

I have not tested the GTK4 version from Debian Testing.