App icon not shown on GNOME under Wayland about signal-desktop HOT 3 CLOSED

This is not a duplicate of #6122

StartupWMClass is set to Signal as the linked issue suggests as a workaround, and the generic app icon is still used.

$ grep StartupWMClass /usr/share/applications/signal-desktop.desktop
StartupWMClass=Signal

from signal-desktop.

I can confirm that I have this issue in Wayland/GNOME as well (Ubuntu 24.04).
Changing the wmclass to signal (lowercase) resolved the issue for me.

I set my local .desktop file to:

[Desktop Entry]
Name=Signal
Exec=/opt/Signal/signal-desktop --enable-features=UseOzonePlatform --ozone-platform=wayland --enable-features=WaylandWindowDecorations --no-sandbox %U
Terminal=false
Type=Application
Icon=signal-desktop
StartupWMClass=signal
Comment=Private messaging from your desktop
MimeType=x-scheme-handler/sgnl;x-scheme-handler/signalcaptcha;
Categories=Network;InstantMessaging;Chat;

from signal-desktop.

@yochaigal That does indeed fix it for me. Running signal-deskop with WAYLAND_DEBUG=1 shows:

[2279573.109]  -> [email protected]_toplevel(new id xdg_toplevel@40)
[2279573.114]  -> [email protected]_app_id("signal")
[2279573.118]  -> [email protected]_title("Signal")

I'll send a patch upstream to the Arch Linux package changing StartupWMClass

from signal-desktop.