The Kanaka Engine service can be upgraded from any version of Kanaka 2.7 and above.
Micro Focus Kanaka for Mac 3.1 can only be installed on macOS Mojave (10.14) and higher. Previous versions of Kanaka cannot run on 10.14+. As such, there is no direct upgrade path for Mac components from Kanaka 3.0.1 and earlier. However, these earlier versions’ components can still be used on earlier versions of macOS, and are compatible with the Kanaka 3.1 Engine.
The Kanaka Engine service includes two DMG files, one containing the Kanaka 3.1 Mac components and one containing the Kanaka 3.0.1 components for use on earlier versions of macOS.
2.7 clients will continue to function as-is because they do not perform certificate validation.
However, once you upgrade a client to version 3.0.1, you will need to replace your server.pem with one that is either signed by a well-known CA or ensure that the client is trusting the root certificate that was used to sign your server.pem.
2.8 clients will continue to function as-is because it is assumed that they have already been configured with a trusted root of the CA that signed the existing server.pem used by the 2.8 Kanaka Engine.