Are you testing that the ports are open with your phone on a cellular network and not WiFi within the same network? Your router may be doing a loop back NAT which “forwards” the ports internally but isn’t necessarily forwarding the ports externally.
Did you change ISPs at all? I think I read that the router was new—is it a router/modem combo? If the ISP has changed it’s possible the new one doesn’t allow traffic on those ports, which is the case for my ISP. No amount of forwarding rules will change that.
If you have a separate modem/gateway and router it’s possible there are firewall rules on the device closer to the WAN in which case you may need to ask your ISP if they can put the modem in “pass through mode” in order to allow the traffic. That’s probably not the technical term for it—I think behind the scenes they either just disable the firewall or put the router address into DMZ, but that description has worked with me in the past with L1 support for them to know what I’m trying to accomplish.
Yes. In the TrueNAS UI you can configure users and groups. You can add users to common groups and set the permissions of the share to allow for group read/write. If all of the clients are on Windows, I wanna say you can set permissions on the share via Windows Explorer which will allow you to make more granular permission changes.
I forget exactly because I only briefly used TrueNAS in this capacity, but there was a community repo you need to add for more apps than the default. I think I remember the default repo having Emby but not Jellyfin, or vice-versa. Someone may be able to help me remember the name of the repo in the comments.
Set up the app as normal for local access and just forward the port from your router to the IP of your TrueNAS instance. There wasn’t anything tricky you need to do beyond a regular installation.