While installing ifconfig correctly install the link: /sbin/ifconfig -> /sbin/ifconfig.net-tools using just "ifconfig" on the command line still calls busybox, as the link: /usr/bin/ifconfig -> /bin/busybox So I think /usr/bin takes precedence over /sbin.
It looks like busybox installs link: /sbin/ifconfig -> /bin/busybox.nosuid which gets correctly replaced by: /sbin/ifconfig -> /sbin/ifconfig.net-tools according to update-alternatives priority. But somehow a second link exists and takes precedence: /usr/bin/ifconfig -> /bin/busybox
Sorry, please disregard this bug altogether, the: /usr/bin/ifconfig -> /bin/busybox was a (wrong) hack, that somebody put in our custom layer. This has nothing to do with oe-core. Sorry again.