Can you please check/confirm that you get the same problem when you first download your custom gadget snap from the store manually and then build it into your image using the ubuntu-image command with the --extra-snaps YOURDOWLOADEDSNAP.snap arg. Note that the ".snap" file extension is needed to ensure the local filesys snap is used.
Can you please check/confirm that you get the same problem when you first download your custom gadget snap from the store manually and then build it into your image using the ubuntu-image command with the --extra-snaps YOURDOWLOADEDSN AP.snap arg. Note that the ".snap" file extension is needed to ensure the local filesys snap is used.