Hey, this is a known issue with cursor-sandbox on Arch Linux. Kernel 7.x+ restricts unprivileged user namespaces by default, so the extension host can’t start and gets stuck on Activating Extensions.
There are two workarounds:
Option A: set setuid on cursor-sandbox:
sudo chmod 4755 /usr/share/cursor/resources/app/resources/helpers/cursor-sandbox
Option B: enable unprivileged user namespaces:
sudo sysctl -w kernel.unprivileged_userns_clone=1
sudo sysctl -w kernel.apparmor_restrict_unprivileged_userns=0
To keep it after reboot, add these to /etc/sysctl.d/99-cursor.conf.
More details and discussion here: "Activating Extensions" message, extensions don't work -- solution
Let me know if either option helped.