Joe is right about NSS for OES 2018. I just installed a brand new OES 2018 server and will post my result of a backup and testing once I get it configured.
I don't expect there to be much of any issues and it should work just fine, but I think I understand your concern. While you and I might think it works just fine, if there is a problem, and you call support, you don't want to here the stock phrase "We don't support OES 2018, have a nice day". This sort of thing pisses off every admin on the face of the planet. I too want this same statement before I put OES 2018 into production, but this won't preclude my own testing. Let me suggest you do the same thing. Install a stand alone OES 2018, new tree and everything, and do some of your own testing.
What I can tell you about Joe is that he is working on getting that statement. I think the only reason it isn't there is that there hasn't been enough testing in the time it has been released, nor has there been a request for it. So since you have asked for it, it is now on the radar.
You can trust Joe.