OpenVPN
Watch out, OpenVPN has tried to monetize with their "Access Server" product. What you want is OpenVPN "Open Source" aka "OSS".
Configure
Install
Debian
OpenVPN (OSS) is available with most distros' package managers.
sudo apt install openvpn
Docker
This seems to be a good starting point here are some instructions. Not going there, Keith "you don't want to mix security concerns", Tom "KISS".