Hello,
we're having the similar problem with safari, we are running OpenVPN on an Ubuntu server, and the problems does not look to me as relevant to DNS. Other browser work as expected. So I am trying to debug this issue.
Till now I found, that something blocks the request from processing and I am searching for some relevant information using wireshark:
There are now entries in OpenVPN log, on server or client.
I doubt it is a OpenVPN problem, rather in Safari, but we need to find a cause and report it to the corresponding party