Yes, I am familiar with portals and what they do: I was exactly wondering if bubblewrap contains something similar — it's been ages since I was involved with Linux system architecture (let's say I am stuck in the SysV init world, and I still go for "service apache2 restart" :)), so it'd be great if there was a quick introduction for someone wanting to use flatpak/snap style sandboxing without the dependency management and distribution channels.