Configuring a VPN server in Windows 10

| I'm using Windows 10 Pro. I'm very familiar with port forwarding configuration. I already had port forwarding configured for Remote Desktop connection with an alternate external port. I tried to do the same thing for this VPN setup (a different alternate port) and specified the alternate port on my iPhone using the public / WAN IP address for my home network, followed by a ":" colon and the alternate port number. It can't connect. I changed the server field to the local IP with no hostname and still couldn't connect.

I know these Arris devices must have the PPTP / L2TP pass-thru options enabled to allow VPN client connections from the LAN. Do those options prevent me from hosting a server on the LAN and making it accessible from the Internet?

Because I access my home PC with Remote Desktop every day, it already has an always-on wired connection with a DHCP reservation so the LAN IP won't change and the port forwarding rules will not break.

Well, I tested on 2 Windows 10 systems and neither of them show anything listening on port 1723 when I run netstat -a

Went through the same setup on a Windows 7 system and it worked perfectly fine. Did Microsoft break this with Win10? Any chance the functionality was intentionally limited or removed?

From the iPhone, I can connect to the Windows 7 test VPN over LAN or WAN (only with the default port number 1723). The iPhone could not connect to the Windows 7 test VPN through any alternate external port number. I configured several in the 4,000s and configured the iPhone with [wanIP]:[port], but it wouldn't connect. I don't know if that's a problem with my router or a limitation of the iPhone VPN client. Perhaps the iOS VPN client doesn't interpret the host:port syntax