Don't run electron/chromium apps with --no-sandbox, that is not safe, you are exposing yourself to the internet.
Canonical decided on ubuntu 24.04 to disable unpriv namespaces in the name of security, in reality they did it to push snaps since that change breaks appimage and flatpak.
Do what linux mint ended up doing and disable the restriction.
kernel.apparmor_restrict_unprivileged_userns = 0' | sudo tee /etc/sysctl.d/20-fix-namespaces.conf
sysctl -w kernel.apparmor_restrict_unprivileged_userns=0
Or better yet just don't use ubuntu, it is just a source nightmares, the uuttils switch even broke one of my appimages...
https://github.com/ivan-hc/AM