You need to choose the type of temperature sensor you'll be using if you haven't already. The three main ones are PTC/NTC thermistors, thermocouples, and RTDs. Each of these categories have many subtypes and compositions that make them useful for specific temperature ranges, etc. Generally people use thermocouples for fast measurements or RTDs for their low-drift, high accuracy.
For thermocouples:
The MAX31855 is an IC for interfacing with thermocouples. There is a version for each type of thermocouple so just choose depending on what you decide to use. Interfacing with it is stupid easy since it requires no setup because it doesn't have registers that need to be set in the first place. It doesn't even have a MOSI pin. It outputs 32 bits including the converted thermocouple temperature, some fault-detection bits, and the internal temperature used for cold junction compensation. It comes in a SOIC package so it's pretty easy to solder by hand.
There is a MAX31856 IC as well but it's much more complicated because it supports many thermocouple types and requires MOSI to setup the registers. It also comes in a smaller, slightly harder to solder package.
For RTDs:
Look into the MAX31865, I haven't used it/made a library for it yet so I can't say much about it.
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