Backup - "Could Not Install" "necessary software"

I’m trying to use the built-in GUI backup program found in “Settings”.

It comes up and indicates that “Necessary Software” needs to be installed. When I try, I get an error window that states:

Error calling StartServiceByName for org.freedesktop.PackageKit: GDBus.Error:org.freedesktop.DBus.Error.Spawn.ExecFailed: Failed to execute program org.freedesktop.PackageKit: Permission denied

When I try to run Deja-Dup from CLI, I get an error message that states:

Failed to execute child process “duplicity” (No such file or directory)

I would really like to use the standard Ubuntu tools for doing a backup. How do I proceed?

I haven’t used those tools, and I’m unsure which repository has duplicity, but I can see it if I run “apt search duplicity” while all of the “/etc/apt/sources.list” are uncommented (run “sudo apt update” after changing anything there). So in theory just run “sudo apt-get install duplicity”.

That first error though looks like it has to run sudo…“Permission denied” implies there is some way of running the application sudo and not as a regular user.