How to install standard OpenWRT packages in recent Teltonika RUTOS versions

Problem

In recent versions of Teltonika RUTOS, the package manager has been replaced with a custom solution.

This means, that you can’t install most of the standard OpenWRT packages using opkg anymore. For example, you can’t install tcpdump using

opkg update
opkg install rsync

Solution

You can still install standard OpenWRT packages by using opkg -e /etc/opkg/openwrt/distfeeds.conf

Example:

opkg -e /etc/opkg/openwrt/distfeeds.conf update
opkg -e /etc/opkg/openwrt/distfeeds.conf install rsync

This works around the limitations imposed by the default system configuration by using the distfeeds (i.e. normal OpenWRT) package feed directly.