Setting the OpenVPN link-mtu to 1100 seems to work around the UDP blocking. Not ideal, but better than TCP with the package loss you experience here.

I live in China and noticed that since a few weeks (starting before the congress) the quality of OpenVPN UDP connections deteriorated severely. Formerly traffic worked fine, but now a ping over OpenVPN has significantly higher packet loss and latency than a direct ping to the same host, while these used to be similar. The connection often drops for 5-10 minutes, after which it is reestablished. A tunnel over ssh now performs a lot better than an OpenVPN connection.

Note that I am using my own servers and non-default ports, not established VPN providers that are easier to block. This behavior occurs on different networks from different ISPs. Additionally, L2TP connections now fail most of the time, while they worked a few months ago.