I just backed up one of my larger appliances, and restored it to one of my smaller appliances this morning. The larger unit had 7 interfaces, the smaller had 6. In the past this would cause issues, however with 9.2.1 the usual restore issues never happened.
I did everything from the physical console of the destination Untangle server, downloading ung.backup from the current production server to the desktop of the Kiosk user and restoring from the local console browser.
I got a JSON error as the restore process started, left the box alone for a few minutes and the browser bounced to a page cannot be displayed error. A minute or so later I was getting the "service unavailable" message. Sometime afterward I was able to log into the UVM again, and refresh the interfaces. After the refresh I've got connectivity on External and Internal interfaces, and module configurations appear to have come along for the ride.
I'll find out later this week if the transition was fully successful, but the usual UT is useless until I reboot after a restore issue is nicely gone. Interface reconfiguration happened without a reboot between restore and reconfig. I rebooted Untangle after the interface refresh for good measure, but only after verifying Internal and External actually light up. While the JSON error starting the restore is a bit of a mess, the restore process appears to be fully functional and may be workable as a configuration migration between hardware in some cases again.
Both Internal and External are responding to pings for devices configured to communicate with them. So far so good, looks like all that DB work is paying off!