The new installer at https://gitlab.com/wikisuite/wikisuite-packages will offer auto-updates, but if you installed before, you need to update manually:
cd /usr/share/webmin/virtualmin-tikimanager git pull
cd /usr/share/webmin/virtualmin-tikimanager
git pull
cd /opt/tiki-manager/app php tiki-manager manager:update
xxxxxxxxxx
cd /opt/tiki-manager/app
php tiki-manager manager:update