Comment by zchrykng

Caddy is great, but doesn't solve the problem I was talking about on its own.

Caddy will get SSL certs automatically if it is exposed to the internet and DNS for that domain points to it, but if you are routing over tailscale exclusively Caddy can't automatically validate the domain names over ACME. There is a Caddy extension for doing DNS based validation, but that puts you back to needing a DNS provider with an API.