The hardware is there (RPi + USB storage). The server software is there (NextCloud, Plex, n8n, etc). What isn't there is the plumbing. The next logical step after this blog post is making your services accessible to your phone over the public net. You'll immediately find yourself mired in domain name registration, VPS management, TLS cert management, dyndns, port forwarding, hole punching, etc etc.

There are lots of great tools that solve some of these problems. I have yet to find one that solves all of them.

I think we need something like Namecheap + CloudFlare + ngrok, designed and marketed for self-hosters and federators. You simply register a domain and run a client tool on each of your machines that talks to a central server which tunnels HTTPS connections securely to the clients.

Mapping X subdomain to Y port on Z machine should take a couple clicks from a web interface.