High temperature is a hardware problem, bad / passive cooling, a bad battery or bad hardware design in general. To some point you can lower the amount of computations and power needed to run your game but even a smooth running game can make a device hot. If this problem is happening specifically on your Galaxy s23 ultra and earlier models, it might not happen on a different series / brand at all.
What I’m saying is, you might be optimizing / removing features for a problem only a small percentage of people have using these models, while in the end it’s a hardware issue and not a problem in your software. There might not be a fix on the Unreal side.
Every device has its own system for temperature management and security in case temps run too hot on parts. Some CPUs can go around 90C and still use passive cooling and there’s nothing you can do about that. Lithium batteries should not get burning hot or they are a serious health hazard with risk of ignition / explosion. I’d contact Samsung about this and hope for model specific advice.