Plex requires a Plex Pass subscription to share outside of your local network. Plex doesn’t allow you to watch media on your local network if your internet service is down, even if you have the Pass, because the service requires a constant connection to the Plex service itself. You can’t use apps on most streaming boxes and sticks without a Pass subscription. Plex records telemetry on all of your viewing habits and shares it with any of your associates who also use the service.

I switched from Plex to Emby a decade ago because of the restriction on local network streaming without an internet connection. My internet service went down and I said to myself “well I can at least watch my locally hosted files on my tv sitting next to the server”. Nope, not allowed. I emailed Plex support about it once my internet was back and they said that wasn’t a bug, it was by design. I dropped it then and there even though I had a lifetime Pass subscription.

Plex doesn’t allow you to watch media on your local network if your internet service is down

It actually does, you can whitelist local IP addresses to bypass plex auth servers.

Good to know, and it would have been nice if that support rep had just told me that ten years ago instead of inadvertently talking me into dropping the service altogether.

Still, for all of the reasons above and more, I’ll never use Plex again. I occasionally help a friend keep his Plex installation maintained and it’s just a shitty service compared to the more open options in my experience. I’ve told him about the better options but his sunk cost mindset (he paid the current lifetime fee) won’t let him migrate.

it would have been nice if that was in the documentation

Its been in the docs for at least 7 years now (check the Last Modified date).