It would probably be good to say that the default path for reading clients has been changed.
The Changelog just tells to readd the clients.
https://docs.software-univention.de/release-notes-4.3-0-en.html#changelog:service:radius
Maybe it would be helpful to update the Wiki too.
https://wiki.univention.de/index.php/RADIUS
New path for clients should be:
/etc/freeradius/3.0/clients.conf
Before it worked with /etc/freeradius/clients.conf .
Because of that there are many dpkg-bak and dpkg-new files within /etc/freeradius .