Openvpn server is not working as intended. Starting the vpn server doesn't add the firewall rule to allow inbound connections. pptp works though, but since it's insecure, I would like to avoid it. nmap output as follows:
The firewall rule is definitely properly configured, otherwise the OpenVPN server wouldn't work for anyone. I note that you are scanning from inside your LAN, which won't test anything - the OpenVPN server is configured to listen to connections on the WAN interface. Therefore, firewall configuration is applied to the INPUT chain, not the FORWARD chain.
The ovpn config files generated by the web ui have some syntax issues, at least as far as importing them into ubuntu's network manager gui goes. The html style formatting for certs embedded in the config file probably doesn't work in ubuntu. I have some other ovpn config files which work. They use separate files for the certs and keys in the same directory, and the ovpn file refers to those files.
This formatting is directly supported by the OpenVPN binary. If Ubuntu does its own pre-processing, then there isn't much I can do about it - the config is designed for OpenVPN, not for Network Manager. This is a limitation in Ubuntu in that case, not a bug in the firmware's generated config.
If is use the ddns name (even from inside the lan), it doesn't allow connection to services (for eg. httpd, ssh) that it normally would if i were to use 192.168.1.1 directly from the lan. I know that this used to work earlier. Edit: Tried changing nat loopback from asus to merlin, but didn't help.
Asus tightened security in recent GPL code. httpd no longer listens to every available interface, it will only specifically bind to the LAN interface, or the WAN and LAN interfaces but ONLY if you set it to listen to both WAN and LAN. Using your DDNS hostname means you are trying to access it through the WAN interface, which is most likely not enabled in your case. This is the intended behaviour, and is far more secure than the old one.