Rapsberry Pi OpenVPN Server
Go here and do as described in the README. It is super simple... if you follow the instructions precisely (RTFM)
I can connect all my OpenVPN capable devices to this server, and it is super simple to create certificates for alle the devices you will allow access !
On a side note: I have installed this on the RPi that is running my PiHole. This gives me (and you if you do the same) the option to use the Ablocking DNS server ANYWHERE !!
See my Pi-Hole for more information ;-)