The only logs from Pangolin are from me accessing https://overseerr.dom.tld. From Plex’s GUI console though, I get this:

Request: [172.18.0.2:46974 (WAN)] GET / (6 live) #18eb GZIP Signed-in
Completed: [172.18.0.2:46974] 401 GET / (6 live) #18eb GZIP 0ms 464 bytes (pipelined: 1)

That 172.18.0.2 is the IP of the Newt container (that subnet is its bridge network, anyway). So it’s making some request to Plex and receiving a 401?

From Mozilla:

The HTTP 401 Unauthorized client error response status code indicates that a request was not successful because it lacks valid authentication credentials for the requested resource.

So what would cause Plex to throw a 401?