Let’s say I setup some subdomains and then point them to my home server via Cloudflare tunnel.
If I use one of those subdomains from my personal PC on the same network as my home server, to watch a movie for example, is all of that traffic going out to the internet and then back? Or does all the traffic stay internal once the connection has been made?
what if I use a separate proxy service locally with a cert and the same domain?
If your client(s) accept irregularly changing remote certs (i.e. they don’t do cert pinning), it should work. If both cloudflare and you use the same CA, it would likely work even with cert pinning. Certainly possible, but increases the complexity of the overall setup.
Cert pinning is pretty uncommon in the self hosting community though, especially when both Cloudflare and Let’s Encrypt have a 90 day validity period and often renews after 60 days.