In the past, I have followed a method of updating OpenWrt devices with an option to restore all installed packages and their configurations without needing to spend hours on reconfiguring and testing everything.
This method uses a simple script run in the terminal to generate a list of installed packages, followed by a web interface to generate a backup file used to restore everything.
As long as the backup file is generated correctly, the restoration process works well, but the problem arises when it isn’t!
On several routers with OpenWrt (24.10.x) that I worked with over recent weeks, I experienced a strange issue that caused me to rethink how I generate a backup file to later use to restore all packages and settings after updating OpenWrt to the latest version.
I discovered this issue the hard way when I wanted to extract a backup to retrieve some configuration from individual files. I noticed that the backup failed to extract correctly.
This was fixed in OpenWrt 25.12; however, I have left it for reference. If you are upgrading from 24.10 to 25.12 and your backup is generated incorrectly, you will not be able to upgrade to 25.12 while retaining packages using Attended Sysupgrade.