Hello Paulyangsmile,
you can check for older versions via
apt-cache policy kix or
yum --showduplicates list kix
If you found your requested version you can install via
apt-get install kix=versionnumber or
yum install kix-versionnumber
If you don't find any older version, you can manually download the package from
https://packages.kixdesk.com/repository
Best regards
Nick