The hardware part is provided by LibreHardwareMonitor. If your hardware isn't detected, you likely need to check if there is an issue open for it in this repo. The other FanControl application also use this library, so you should have the same result with both.
You can test the sensors program to see detected pwm sensors on your machine. If it is not present here, then it will also not show in the app. You can open an issue in this repo if this is the case.
In my experience, a lot of laptop fans will not be detected, and NVIDIA is not supported (we need root access for it so no compatible with flatpak).