Maybe I'm missing something, but if your friend's router had the capability to, would it not be easier to just set up a WireGuard tunnel directly on the router to VPN straight into their local network? Then you're able to just access the UI through your browser remotely, without reliance on any server at all.
I have a TP-Link with this functionality. Not sure quite how widespread this is in 2025.
Great initiative, terrible AI-written article with clickbait Elon ads.