Hot Spot

[Foldbak]

I have a grandfathered unlimited data plan. How can I hack the hot spot?

 

[svim]

First off you need to root your device, which may or may not be readily done depending on your device and which version of Android it's running. Also while it's often touted as a magic fix for everything, in reality rooting your device has a lot of consequences that need to considered:
https://phandroid.com/2019/02/23/5-reasons-why-you-shouldnt-root-your-android-smartphone/
Basically, root access allow one the ability to do a lot more things, it does not however give them the knowledge that goes along with that added responsibility, so at least go into the process of rooting being aware of the pluses and minuses.
Anyway, once that's done, there are different ways to get tethering working on your device if it's not already enabled. A couple of examples being:
https://www.howtogeek.com/263785/how-to-use-androids-built-in-tethering-when-your-carrier-blocks-it/
or maybe this more dated one will work out for you:
https://android.gadgethacks.com/how-to/enable-free-wifi-tethering-android-marshmallow-0167832/
But always keep in mind that while you might be able to hack your own device, you can't 'hack' your cellular carrier's connectivity. Your carrier manages its cellular network and monitors your account activity so if it detects your hotspotting, it may take action, note that grandfathering preserves your previous bandwidth allowances, it doesn't allow you to wiling violate your Terms of Services with them.
But even if this does happen (as long as you don't get too abusive about using your mobile data it probably won't) you'll probably just get a vaguely worded email or text message about how 'suspicious' activity has been detected in your account and that you should take steps to correct the problem. A lot of this also depends on your carrier, most of them put up with a lot of stuff just to keep you as their customer.

 

[Foldbak]

Thanks for the fast response. So if I understand you correctly I can achieve this but AT&T can tell the difference between data usage on the phone and data usage hot spotting.
Here's what I'm trying to achieve. I take my trailer to the beach and want to watch Netflix at night. If I could connect to my phone I be covered. If I had a WiFi router could I screen share?

Update. I just did a screen share with my LG TV not connected to the internet but is was a bit jumpy. So I imagine screen sharing on 4G it's going to be worse. Bad coverage at the beach...

 

[svim]

Depending on what apps you're using while tethering it may or may not be easy to do routine packet sniffing on your online traffic so if there's an occasional detection of some violation of their ToS it's pretty unlikely you'll get any kind of warning. Again, just try to be use some moderation and be cognizant of the apps and things that go through your hotspot WiFi.

A typical off-the-shelf wireless router needs a wired input (coax for cable, phone line for DSL) so that might not be an option for your example in your trailer. You could get an AT&T mobile hotspot, but those a bit pricey. Just curious but how much does AT&T charge for hotspotting in your existing account with them?

If you're getting jumpiness and/or buffering issues, is your LG TV connecting to your WiFi over a 2.4GHz band network or a 5GHz one? A basic rule of thumb is 2.4GHz provides longer range and penetrates basic housing construction materials (wood, drywall, etc.) while 5GHz provides faster bandwidth. Also, since the content you where streaming was being mirrored, was it pretty high res content? That's often a big factor when viewing streaming content either online or locally.

 

[electricpete]

there is no root available for us / snapdragon version of the galaxy S9+.

fwiw my s9+ screen mirrors smoothly using Samsung smartview to my 760p roku tv while both are on wifi (my phone screen resolution is set to 760p). maybe try going to 1080 or 760 resolution to see if it helps