Ubiquiti removed keytool (and java) from recent releases of Unifi OS. This moves from keytool to openssl's native pkcs12.
Tested on Unifi Dream Machine which runs Unifi OS and a built-in Unifi controller.
Also added backup of existing files prior to change in case anything goes wrong, and update system configuration with compatible ciphers.
The current script is already broken due to Bind 9.16 -> 9.18 changes
due to their renaming scheme for primary/secondary so do not rely on the
compat layer (which was also broken for other reasons).