Thermal imaging LWIR differs from CMOS and CCD NIR

There are tutorials online that say you can convert a color camera to an infrared camera.  To be clear, you can remove the IR cut filter and improve the infrared sensitivity of a CCD or CMOS camera.  However, you will not be able to measure temperature in the way that a FLIR thermal camera can.
This is because the thermal cameras detect Long Wave Infrared (LWIR) between 7500 nm and 14000 nm.  Standard video cameras can detect light between 310 nm and 1000 nm (nanometers).

In this chart of a Sony IMX367 color sensor (provided by Matrix-Vision.com), the IR cut filter is indicated in magenta.  Removing the IR-cut filter will allow the R G and B photo-sites (pixels) to absorb energy in the infrared spectrum.

https://www.matrix-vision.com/usb3-vision-camera-with-hi-res-sony-cmos-sensors-mvbluefox3-4.html?camera=BF3-4-0315ZC&col=1&row=pregius

But if the goal is to detect more NIR, just use a monochrome image sensor.  That way the RGB Bayer filter is not limiting any of the pixels.