You may try some tools
sudo apt install thermald tlp indicator-cpufreq
Thermald and tlp just run, no additional configuration needed.
Indicator-cpufreq is an application that allows you to choose which Mode to run in, such as Performance or Power-saving.
I would also recommend cleaning out your vents with a can of air, just to be on the safe side.
Dust and Lint insulate as well as blocking airflow. Fan speed is less important that heat exchange is. If even Windows is cranking up fan speed - Ensure that the notebook is kept elevated on flat surfaces, never placed on a chair or blanket.
So i would not just look at the software side alone. Can you run the AIO without covers, maybe allow some external airflow to pass over it while you work? See if that helps. If so, then you know where to look..