This is neat. I don’t use Caddy, but I wondered if something like this would be possible with Traefik. It looks like the Tailscale folks specifically released a Go module[0] that allows Caddy to interface with their certificate provisoning service. I imagine this could be re-used in other tools to achieve the same thing.

[0] https://github.com/tailscale/tscert

You can make traefik grab wildcard certs and those can then be used for whatever you want