The kiosk runs under NoNewPrivileges=yes (WebKit bwrap needs it). sudo
and nsenter both fail because they need privilege escalation which the
flag blocks. systemd-run --pipe spawns a SEPARATE service unit as root
in its own process tree, connected via stdin/stdout pipe. Not a child
of the kiosk process → NoNewPrivileges doesn't apply.
Also: enable rauc.service in pi-gen chroot (was never enabled → RAUC
daemon not running → rauc install fails → OS update silently broken).