Roon ARC connectivity issues from outside network

Roon Core Machine

macOS Monterey version 12.6
3.3 GHz Dual-Core intel Corei7
16 GB 2133 MHz LPDDR3

Roon version 2.0 build 1128 production

{
“connectivity”: {“status”:“NetworkError”,“status_code”:504,“error”:“error: Error: ETIMEDOUT, response code: undefined, body: undefined connected? undefined”},
“external_ip”: {“actual_external_ip”:“174.92.214.74”,“router_external_ip”:null},
“natpmp_autoconfig”: {“status”:“NotFound”},
“upnp_autoconfig”: {“server_ip”:“192.168.2.1”,“found_upnp”:true,“error”:“Did not find UPnP service with WANIPConnection on network”}
}

Networking Gear & Setup Details

Canada - Bell Home Hub 3000
Roon core software running on MacBook Pro via wifi

Connected Audio Devices

Apple HomePods

Number of Tracks in Library

6210 tracks

Description of Issue

Cannot connect to Roon ARC outside my home (I can connect when I am at home and on the same network).

I contacted my service provider to see how to open a port - apparently it is not possible to configure the router.
How do you suggest we proceed to resolve this issue?

This person managed to do so

Yes, have the same issue. And I tried that suggestion, but still ARC does not connect. Basically I have tried all suggestions on the help page.
My, Asus GT-AX11000, is allowing port forwarding, I have set to the port to the exact same number as in Roon.
My NUC 11 PAHi3 (11th Gen with Intel HD audio) is running audiolinux and I have confirmed with the vendor that it allows me to access it from outside. So he concluded it is a Roon issue.
Any suggestion on how to connect Roon ARC?

Here is my error message

{
“connectivity”: {“status”:“NetworkError”,“status_code”:504,“error”:“error: Error: ETIMEDOUT, response code: undefined, body: undefined connected? undefined”},
“external_ip”: {“actual_external_ip”:“101.78.83.135”,“router_external_ip”:null},
“natpmp_autoconfig”: {“status”:“NotFound”},
“upnp_autoconfig”: {“server_ip”:“192.168.50.1”,“found_upnp”:true,“error”:“doaction request return statuscode: UnknownError”}
}