I took the bait.
“The goal of Landlock is to enable restriction of ambient rights (e.g. global filesystem or network access) for a set of processes. Because Landlock is a stackable LSM [(Linux Security Model)], it makes it possible to create safe security sandboxes as new security layers in addition to the existing system-wide access-controls. ... Landlock empowers any process, including unprivileged ones, to securely restrict themselves.”