I'm using an L2TP VPN which is built into Windows, I'm not sure whether that uses TCP or UDP. I spent a few hours trying to set up OpenVPN a while back and couldn't get it to work (and I'm a very experienced user). The official guides were out of date and not detailed enough, and even once I finally got all the certificates sorted and all necessary ports open and checked, it wouldn't even connect, let alone authenticate.
L2TP uses udp.
I recall that setting up OpenVPN was hard
Come on that's not really hard.
Just built a new box for one of our customers last week.
Did you try on linux or windows?
At first I ran the OpenVPN server in my asus router. This was easy to set up. Because of the heavy encryption of the datastream the router cpu was overloaded. Because of that I installed OpenVPN server on a windows machine. It did not work. Had some kind of routing issues. Ended up with lowering the encryption and kept OpenVPN server in my router. Client setup was not hard