Flatpak is a popular means to distribute software on Linux that installs and runs in a sandbox for each application. This is particularly useful when an application needs a newer GLIBC / GLIBCXX than the system has, which is often the case on RHEL and HPC systems.
It can be convenient to open a sandboxed shell in a Flatpak app’s sandbox. For example, to open a shell in the GNU Octave Flatpak sandbox:
flatpak run --command=sh org.octave.Octave
This can be useful to build further applications with CMake using a Flatpak program, for example CMake with GNU Octave.