Add ntfy at ntfy2.rubenhensen.nl on the home cluster, pointed straight at
the home IP like s2. s2 now alerts on mail and on s1 through it. The
home services are left to s1, which sees them from outside.
ntfy denies everything except the provisioned user. The user, its
password hash and the Gatus token come from Vault kv/ntfy.
Gatus with sqlite history, checking every public service plus its twin
s1.rubenhensen.nl on Hetzner. Replaces the GitHub-hosted Upptime page.
DNS gets s1 (Hetzner) and s2. s2 points straight at the home IP rather
than through the Hetzner tunnel, so it stays reachable when Hetzner is
down.
gatus/README.md explains how to read the two pages and writes down the
plan for a single self-hosted failover URL (PowerDNS LUA records).
Ruben Hensen