Thermistor returns correct value on Arduino Nano, completely fails on Arduino Uno Wifi Rev 2?
The Arduino UNO WiFi Rev2 defaults to an internal analog reference of 0.55V where the classic (non-&quot;Every&quot;) Nano defaults to the external VCC voltage as a reference, which is usually around 5V, often a little lower because of the diode it uses between USB and &quot;5V&quot;.
Either you need to be using the same voltage reference by selecting a common one with analogReference, or you need to use different references and calculate differently (or provide different values to the thermistor library) according to each reference.
If you've been using the VCC on the normal Nano board, you could try analogReference(VDD); on the UNO Wifi Rev 2.  This isn't necessary a great way to do it (probably using internal references would be better), but it is a simple way to get similar results on a UNO Wifi Rev2 without changing more than a single line to set the reference.