I've recently updated the MT-3000 to firmware v4.8.1. It looks like any local changes stored in the filesystem are wiped when the flash happens. i.e. Any config files stored in /root are wiped; only the entries from /etc/config are kept.
Also all applications previously installed with opkg / luci are wiped. I had some cron scripts relying on a third party package being present and after the update the application was no longer present.
I assume that /etc/wireguard is also wiped?
Is this the expected behaviour? It would be ideal if the installed third party applications were kept, and also that /etc/wireguard was kept.
As new firmware versions may introduce new features, update or replace dependencies, or remove outdated components, we do not retain third-party plugins/files during an upgrade.
This is to prevent potential conflicts that could arise, which might otherwise render the device unstable or even unusable.
It won't include a list of the addn'l pkgs/binaries you've installed but you're going to what to look into /etc/sysupgrade.conf before you start pulling backup tarballs in LuCI.