Interesting question - I just used letsencrypt.org for the first time a couple days ago (on an Apache2 server) but wanted to figure this out. But this isn't the place to post the answer, probably, so I started a thread in the cnMaestro forum: http://community.cambiumnetworks.com/t5/cnMaestro/on-premises-real-SSL-certificate/m-p/70948#M1747
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