Tailscale is exponentially worse, though. Not only would I have ask them to go to Jellyfin and sign up and log in, I would have to explain that they can't do that until they've installed the Tailscale app (which I have to explain because most non-techies do not know what a VPN is). Tailscale requires its own account, so they have to first sign up to that, and I have to add them as an external user first.
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.
Yea, for clarity this is what i was describing. I use Porkbun's API and the Caddy instance isn't reachable from the internet, only local and over tailscale