NRFConnect SDK 3.2.4: ZAP GUI not launching with command `zap-gui` (no errors)

[vkm]

NRF Connect extensions running within a flatpak VS Code on Ubuntu 25.10.

First of all, fixed the certificate not found issue that some folks have reported in other questions when trying to download/install zap by running:

python -m pip install pip-system-certs

But in the NRF 3.2.4 SDK terminal, within VS Code, when I run `west zap-gui`, I see the below as the terminal output. The GUI for ZAP doesn't open, but also no error messages appear in the console. Has anyone seen this before? How can I troubleshoot this to figure out what the problem is?

sh-5.2$ west zap-gui
Using ZAP file: ~/Documents/dev/light_bulb/src/default_zap/light_bulb.zap
Using ZCL file: ~/ncs/v3.2.4/modules/lib/matter/src/app/zap-templates/zcl/zcl.json
Using app templates: ~/ncs/v3.2.4/modules/lib/matter/src/app/zap-templates/app-templates.json
ZAP installation directory: ~/ncs/v3.2.4/modules/lib/matter/.zap-install
Current ZAP version: 2025.10.23
Found ZAP 2025.10.23 (up to date)
output: 
sh-5.2$

[Øyvind]

Hello, 

NRF Connect extensions running within a flatpak VS Code on Ubuntu 25.10.

Please note that Ubuntu 25.10 is not an official supported operating system as per latest documentation. But our developers point out a plausible cause related to AppArmor. Please issue the following command for a work-around:

sudo sysctl -w kernel.apparmor_restrict_unprivileged_userns=0

Kind regards,
Øyvind

[vkm]

Thanks, wish it worked, but still the same (lack of error) and it closes. I did check dmesg, and when trying to launch zap-gui I get this error. Sharing it here for posterity/web search.

traps: zap[2141531] trap int3 ip:5e6c12f37eaa sp:7ffd964ceb10 error:0 in zap[5e33eaa,5e6c0f0ec000+864a000]

I have SDK 3.1.1 with matter utils working for now, so I'll stay on the older version. That took a little work which I should post somewhere, maybe on a different thread.

[vkm]

Though not ideal, I edited ~/ncs/v3.2.4/modules/lib/matter/scripts/west/zap_gui.py adding line 92 (showing 91-93 for context):

                cmd = [zap_installer.get_zap_path()]
                cmd += ["--no-sandbox"]
                cmd += [zap_file_path] if zap_file_path else []

That worked to get it to launch and seems to work. I know --no-sandbox isn't ideal, but given a lot of change has been happening in releases on ubuntu around user and kernel level namespaces and the chrome sandbox isn't keeping pace, I can accept this for now.

Separately since I run the IDE in a flatpak, I also do the following, to allow the NRF Connect plugin to launch new GUI tools like zap-gui. Sharing it here in case someone else is running a modern linux distro and running into issues. Hopefully one day someone finds a more elegant solution.

(In a host terminal file): cp $XAUTHORITY ~/.xauth

(In a VS Code NRF Connect SDK Terminal): export DISPLAY=:0.0; export XAUTHORITY=~/.xauth