The layer 2 functionality is still present but hidden. It is on the way out. We are hiding it because it is extremely difficult to get it to work reliably in all situations and is extremely hard to support. Besides that, it really is the worst way of setting up VPN. You should be using layer 3. Throwing a Windows Server in the mix also does not make things easier in that regard either. Basically you've chosen one of the least desirable combinations of settings.
You should be using Layer 3 routing mode. It will be easier and more reliable.
Here's how to enable Layer 2 if you really still want to do this:
https://openvpn.net/vpn-server-resources/advanced-option-settings-on-the-command-line/#choosing-layer-3-routing-or-layer-2-bridging
