flatpak-xdg-utils contains a number of commandline utilities
for use inside Flatpak sandboxes. They work by talking to
portals.

Currently, there is flatpak-spawn for running commands in
sandboxes as well as xdg-open and xdg-email, which are
compatible with the well-known scripts of the same name.

Everything else in xdg-utils is not provided. That includes
xdg-settings and xdg-mime as they deal with settings that
Flatpaks do not have access or control to.