Earlier quoted context omitted.
Flatpak is focused on GUI apps only, for CLI apps you'd use whatever you're used to.
What makes a GUI app worth containerizing and CLI tools not worth containerizing?
Agree 100%, and podman/docker already exist.
The way I do it is to use [Distrobox](https://github.com/89luca89/distrobox) to use whatever distro's userspace has the thing I need (I use either the newer devel version of ubuntu or alpine), so if I need a newer version of a CLI tool I can get that without conflating it with the OS layer. It's a similar workflow to how OSX and Windows WSL do it.
So I'm just using the normal debian packages for everything, except it's in a nice split out container just for my userspace with access to all my data. This is the workflow from Fedora Silverblue, openSUSE's MicroOS and EndlessOS, which kind of forces you into the cloud native mindset, but you can run any distro this way.