I have installed LineageOS using PINN on my raspberry pi 3 and it runs fine, but I started worrying about high temperature. You see, when I use Raspbian or RecalboxOS, it warns me with a temperature icon when the temperature is too high. When I am using Lineage, I don't get any under voltage warning, probably meaning that I won't get high temperature warning too. So, is temperature controlled by hardware or software? If it is controlled by software, then I will need to be careful.
Temperature warning is conrolled by the Raspberry Pi firmware.
If the temperature of the SoC is between 80C and 85C, you will see the "Over temperature warning". If the temperature of the SoC is over 85C, the ARM core(s) and the GPU will be throttled back in an attempt to reduce the core temperature.
Whilst hitting the temperature limit is not harmful to the SoC, it will cause CPU throttling. A heatsink can help to control the core temperature and therefore performance. This is especially useful if the Pi is running inside a case. Airflow over the heatsink will make cooling more efficient. [..]
With firmware from 12th September 2016 or later, when the core temperature is between 80'C and 85'C, a warning icon showing a red half-filled thermometer will be displayed, and the ARM cores will be throttled back. If the temperature exceeds 85'C, an icon showing a fully-filled thermometer will be displayed, and both the ARM cores and the GPU will be throttled back.