nginx and certbot were designed assuming they lived on the same host
as the app. They don't - a dedicated proxy Pi terminates TLS and
forwards plain HTTP over the LAN. Kestrel now binds 0.0.0.0 instead
of localhost, the whole certbot procedure moved to the proxy Pi's
side, and pi-main gets a firewall rule restricting the backend ports
to just the proxy Pi's address - otherwise binding all interfaces
would let anything on the LAN skip the proxy's TLS entirely.
Sluijsens
50c1a5106d