EX15W basic Windows VPN setup

First, I RTFM and followed the setup instructions. I even followed the video on youtube - https://www.youtube.com/watch?v=Az4QY9RrwNM

This is what I’m trying to accomplish:
On a windows device, I want to open a VPN connection to the EX15.
The EX15 has a single wired connection to a switch with DHCP.
In a browser on my computer, I want to enter the IP address of the remote device to access the web interface of the remote system.

In theory, that sounds simple to me - not much info in the Windows VPN setup, the Digi however, has Diffie Hoffman Groups (what?!)
Is there a PDF out there that tells the correct minimum settings to accomplish this? The above video seems like a perfect fit for this issue, but it seems to be missing something.
We’re even prepared to Venmo someone to AnyDesk/TeamViewer into the Digi to set it up.
Any suggestions?

Hello,

Quick question - does your EX15W have a Public mobile IP address? I ask because this is a requirement for this video/setup to work. Assuming that your EX15W has a SIM card and it has cellular (not wired) Internet access, whether or not your mobile IP address is Public (or Private / NAT’d) is ultimately a question about the SIM card and its data plan / capabilities.