I assume it doesn't, but thought I'd ask.
I really like the principles behind both gentoo and flatpak, but right now I can only do the gentoo way or the flatpak way (and I've opted for gentoo's for now).
What I'd love to have from flatpak:
- container like sandboxing and isolation
- customizable sandboxing and permissions
What I'd love to have from gentoo:
- powerful build system building packages from source
- global declarative management of compilation options
- easy patches
- easy to add packages that aren't in repos
- support for many architectures or setups
But Flatpak has its fancy "portals" to connect each app with the specific resource it needs which you don't get with Docker.
Also if the goal is to limit access of apps you don't want to fully trust, I think Docker doesn't have the appropriate security properties. Here's a quote from the readme for Bubblewrap (the sandboxing tool that Flatpak and Nixpak use),
in theory shouldn't it be possible to use bubblewrap and the xdg-desktop-portal project to hack together only the sandboxing bits of flatpak while leaving out ostree/distribution
you might run into this though: https://github.com/flatpak/xdg-desktop-portal/issues/737