README from https://ungoogled-software.github.io/ungoogled-chromium-binaries/releases/linux_portable/64bit/ instructs me, before I run ungoogled-chromium, to setup my system by using the user namespace sandbox so that the browser's sandboxing will work.How do I go about this?
My environment: Ubuntu Desktop 22.04 LTS. Let's say that the username of my admin-user is leo.