Hi Kurt I do not think that this is coturn's problem. OpenSSL 1.1.0 is not backward compatible with previous versions, and this is their problem. Having two separate code versions for pre-1.1 release and for 1.1 is not practical. I'd suggest that you have to contact openssl folks and ask them to fix their new version - it is still beta and they must be able to fix it.
Thanks Oleg