Black screen / Error 108 connecting to Pop!OS 24.04 COSMIC (Wayland)

[peddanet]

Hi,

I’m trying to connect from a Windows client (NoMachine 9.0.188) to a Pop!OS 24.04 machine running the COSMIC desktop (Wayland compositor,
written in Rust by System76).

Hardware: HP Envy 13, NVIDIA MX250, Driver 580.159.03
NoMachine server: 9.0.188

**Symptoms:**
– Connection authenticates successfully (user logs in)
– Physical monitor shows NoMachine notification “desktop is being viewed”
– Windows client shows black screen only
– After ~10 seconds: Error 108 (connection lost) or Error 10b (connection reset by peer)

**What I have tried:**

1. WaylandModes egl,drm,compositor → black screen, Error 108
2. WaylandModes compositor,drm → black screen, Error 108
3. WaylandModes drm → black screen, Error 108
4. EnableEGLCapture 1 (via –eglcapture yes) → no change

**node.cfg relevant settings:**
WaylandModes compositor,drm
EnableEGLCapture 1
DefaultDesktopCommand “/usr/bin/start-cosmic”

**server.cfg relevant settings:**
PhysicalDesktopMode 2
CreateDisplay 0

**Root cause identified:**
xdg-desktop-portal-cosmic fails with repeated dbus errors:

ERROR cosmic_config::dbus: Failed to create watcher for com.system76.CosmicTk
ERROR cosmic_config::dbus: Failed to create watcher for com.system76.CosmicTheme.Mode
ERROR cosmic_config::dbus: Failed to create watcher for com.system76.CosmicTheme.Dark

Also: xdg-desktop-portal cannot connect to PipeWire:
Failed connect to PipeWire: Couldn’t connect to PipeWire

The service xdg-desktop-portal-cosmic.service does not exist as a systemd user service, only as a dbus activation file:

/usr/share/dbus-1/services/org.freedesktop.impl.portal.desktop.cosmic.service

**Question:**
Does NoMachine 9.x support the COSMIC Wayland compositor via xdg-desktop-portal? If yes, what is the correct configuration?
Is there a workaround for the PipeWire connection failure when xdg-desktop-portal is started outside the COSMIC session context?

Thank you

[Author]

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