Are you using a *.duckdns.com domain or is that only for Dynamic DNS pointed to something like jelly.domain.com? I’m not sure if you’ll be able to get a cert in the former scenario.
Your router won’t let you access it because you’re trying to connect from your internal network to your external network, so you’re just connecting in a loop and not getting routed properly. This could work if you had a firewall that would let you set up a loopback NAT, but my guess is your router won’t let you setup NAT rules like that.
You won’t be able to get a certificate using a local domain from a public certificate authority (like Let’s Encrypt). You would want to define the FQDN you want to use, like jelly.domain.com, and generate the certificate for this domain. You can do this manually with certbot and import the certificate to jellyfin, or put jellyfin behind a reverse proxy like Caddy or Nginx and let it handle automatic renewal for you.
The local DNS entries would then redirect internal reauests for jelly.domain.com to your local server, which presents the same certificate for jelly.domain.com regardless of whether you’re accessing it via the private or public IP.
The bonus of using something like Caddy is being able to open a single port on your router for every service. I have multiple services all accessed via the same port, and Caddy just reads the requested subdomain (jelly.domain.com, nextcloud.domain.com, etc) to route the traffic to the corresponding local server. This lets it handle every cert for all services with no manual steps needed for any of them after the initial setup, and reduces your attack surface by only having one port open.
qjkxbmwvz@startrek.website 1 week ago
So long as your certs are for your fully qualified domain there’s no problem. I do this, as do many people — mydoman.com is fully qualified, but on my own network I override the DNS to the local address. Not a problem at all — DNS is tied to the hostname, not the IP.
sugar_in_your_tea@sh.itjust.works 1 week ago
Can confirm, I do this as well for my local services (especially important for Jellyfin), I just point my local DNS server at my local IP and everything works perfectly.
qjkxbmwvz@startrek.website 1 week ago
Another fun trick you can play is to use a private IP on your public DNS records. This is useful for Jellyfin on Chromecast for instance — it uses 8.8.8.8 for DNS lookup (and ignores your router settings), so it wants a fully qualified domain name. But it has no problem accessing local hosts, so long as it’s from 8.8.8.8’s record.
sugar_in_your_tea@sh.itjust.works 1 week ago
I suppose, but then you’re kind of screwed if you want to access Jellyfin outside of your network. I suppose you could use a VPN, but it’s probably easier to just not use the Chromecast (or just accept that it’s going to hit the WAN regardless).