Help with nginx & jellyfin

So I’m just getting started with selfhosting things, and I have a minor problem which I’m having some trouble solving, as I keep getting a connection refused error when trying to connect:

send() failed (111: Connection refused) while resolving, resolver: 127.0.0.1:53

I run a jellyfin server on a NUC - it works well and is accessible on the private network. I want to have a public URL for this server - and other stuff, eventually.

Here’s my setup

• I have a subdomain - jellyfin.mydomain.com - pointed to the external IP for my router
• I have the router set up to allow remote access, and port forwarding directing all port 80 traffic to my public ip > port 80 on the server
• On my server - running ubuntu - I installed nginx
• I used the official jellyfin nginx config for access from a subdomain
• I edited the server_name variable to match my subdomain

Now, whenever I access the subdomain in a browser I get a 502 Bad Gateway error. The /var/lof/nginx/error.logshows:

<span style="color:#323232;">2024/05/10 08:26:37 [error] 95335#95335: send() failed (111: Connection refused) while resolving, resolver: 127.0.0.1:53
</span><span style="color:#323232;">2024/05/10 08:26:37 [error] 95335#95335: send() failed (111: Connection refused) while resolving, resolver: 127.0.0.1:53
</span><span style="color:#323232;">2024/05/10 08:26:42 [error] 95335#95335: send() failed (111: Connection refused) while resolving, resolver: 127.0.0.1:53
</span><span style="color:#323232;">2024/05/10 08:26:47 [error] 95335#95335: send() failed (111: Connection refused) while resolving, resolver: 127.0.0.1:53
</span><span style="color:#323232;">2024/05/10 08:26:52 [error] 95335#95335: send() failed (111: Connection refused) while resolving, resolver: 127.0.0.1:53
</span><span style="color:#323232;">2024/05/10 08:26:57 [error] 95335#95335: send() failed (111: Connection refused) while resolving, resolver: 127.0.0.1:53
</span><span style="color:#323232;">2024/05/10 08:27:02 [error] 95335#95335: send() failed (111: Connection refused) while resolving, resolver: 127.0.0.1:53
</span><span style="color:#323232;">2024/05/10 08:27:07 [error] 95335#95335: *69 jellyfin could not be resolved (110: Operation timed out), client: 193.29.107.173, server: jellyfin.mysubdomain.com, request: "GET /web/ HTTP/1.1", host: "jellyfin.mysubdomain.com"
</span>

I have almost no experience with networking, linux, or nginx :D So I am sure the problem is obvious to someone else…

Can you help?