I have this same question.
I would say there certainly was a recommended version when we deployed FortiNAC here about 10 months ago. I stood up a VM with 9.2 and was told to start over with 9.1.7 as it was recommended because of stability reasons. So the question to start with is if Fortinet is helping with a new deployment which version would be chosen and why. Then let's go from there.
Thank you in advance for your recommendation and insight.
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