FWIW, I have customers that maintain mixed AIX and Linux clusters using the native NTP daemons. It's very straightforward to maintain both config files from the same set of variables using just about any system management tool.
I'm also sure I would not want to troubleshoot a non-native NTP daemon on AIX, even if chrony were to support the platform. NTP is a very "rich" protocol and the linkage between it and the system is not trivial.
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Stephen L. Ulmer
Enterprise Architect
Mainline Information Systems