Tailscale Funnel broken when using NordVPN simultaneously

### What is the issue?

I am experiencing a persistent conflict where Tailscale Funnel stops working for external users whenever I activate my secondary VPN for torrenting. This issue began recently and prevents remote access to my Jellyfin server while the VPN is active.

What works:

Funnel works correctly when the secondary VPN is off.

Funnel works for devices connected to my Tailscale network (inside the tailnet).

What doesn't work:

Funnel stops working for external users when the secondary VPN is on.

tailscale funnel status shows the Funnel is active, but external connections fail.

What I've tried (without success):

tailscale funnel reset and tailscale serve reset

Restarting the Tailscale service (net stop Tailscale / net start Tailscale)

Switching the Funnel to port 10000 (tailscale funnel --bg --https=10000 8096)

Verified "Allow Incoming Connections" is enabled in Tailscale settings

Confirmed no other service is using port 443 (netstat -aon | findstr :443)

Diagnostic Evidence:

tailscale funnel status:

text
# Funnel on:
# - https://desktop-a563ddb.tail56ffe1.ts.net
tailscale funnel status --json:

json
{
"TCP": {
"443": { "HTTPS": true }
},
"Web": {
"desktop-a563ddb.tail56ffe1.ts.net:443": {
"Handlers": {
"/": { "Proxy": "http://127.0.0.1:8096" }
}
}
},
"AllowFunnel": {
"desktop-a563ddb.tail56ffe1.ts.net:443": true
}
}
netstat -aon | findstr :443 (Funnel only listens on Tailscale IP, not 0.0.0.0):

text
TCP 100.126.10.32:443 0.0.0.0:0 LISTENING 13132
tailscale bugreport: [Include ID after running the command]

Additional Context:
This issue appears similar to the "phantom" configuration problem described in other reports, where a Funnel configuration gets stuck in the Tailscale control plane. The Funnel was working simultaneously with my secondary VPN for months before this started. I suspect the VPN is preventing Tailscale from binding to the public network interface, or there is a routing conflict when both VPNs are active. This behavior matches the symptoms reported in issue #20739.

### Steps to reproduce

_No response_

### Are there any recent changes that introduced the issue?

_No response_

### OS

Windows

### OS version

11 25H2 (10.0.26200.8875)

### Tailscale version

1.102.3

### Other software

NordVPN

### Bug report

BUG-4da3229f55f6d5bb049716924ed5c3d8f203ca24e69753099bd323b547a00b29-20260908021526Z-825a03be3238231f

Start by reviewing issue #20739 and the attached Tailscale bug report, then reproduce the failure on Windows 11 with NordVPN enabled. Compare Funnel behavior with NordVPN off and on, using the reported funnel status, JSON configuration, and port 443 listener as initial evidence. Done means external Funnel connections work while NordVPN is active without breaking tailnet access.

Written by the indexing model from the issue text.