How to create and install a flatpak from USB on an older version

Question

The flatpak documentation describes the process of exporting an app using the create-usb command. I would like to use this procedure to deploy an app to offline systems that are running an aging version of flatpak. Specifically, the target systems have flatpak 1.0.9.

On my build system (flatpak 1.15.4), I can successfully export by doing

• flatpak-builder --user --install --force-clean build-dir my.app.json
• flatpak remote-modify --user --collection-id=org.flathub.Stable app-origin
• flatpak create-usb --user build-dir my.app

I then tar it up and transfer it to the target. On the target I extract the tarball, then:

• flatpak remote-add --user --if-not-exists app-origin file:///path/to/exported/dir
• flatpak remote-modify --collection-id=org.flathub.Stable app-origin
• flatpak install --user app-origin my.app

That last command fails with error:

1 metadata, 0 content objects fetched; 592 B transferred in 0 seconds
error: Refspec 'dmc:ostree-metadata' not found

I have seen various permutations of the commands needed to install on the target (flags like --sideload and --sideload-repo), but those don't seem available on flatpak 1.0.9. If anyone has a procedure that would work, or if anyone knows how to decipher that error message, please let me know. Thanks!