Please add a section / link about the legacy (3.x) documentation to the opening page. Something similar to this:
## Legacy Administration Guide
You can find the 3.X version of the syslog-ng administration guide on the [One Identity support portal](https://support.oneidentity.com/syslog-ng-open-source-edition/).
Please add a section / link about the legacy (3.x) documentation to the opening page. Something similar to this: