Build a7ac62f4 has the fix for OpenVPN. I have done a core update again with my system and confirmed that the fix is in place.
Creating a new client connection worked without any issues.
Tested the new client connection with my laptop and was able to successfully make a connection. Old client connection also still functioned.
So this issue with OpenVPN looks to have been fixed.
Please can some other users re-do the Core Update 189 Testing update, as per my link in my previous post, to confirm that this now fixes the issue that was identified.