Is there support for a temperature probe wired directly to a Raspberry Pi GPIO or I2C? If not, there should be since it shouldn't be necessary to use an Arduino for the task.
I2C and SPI yes, direct no. I am investigating Astroberry DIY as a way of integrating different temperature solutions including internal as well as external.
No, that would mean to write an INDI driver. I have currently no plans to do this, as I am building an Ardufocuser, which will also include a temperature sensor...
So the Astroberry DIY driver is excellent, but is not compatible with my motor driver, a Waveshare Stepper Motor HAT that is based on the DRV8825. Perhaps I will ask Radek to add support for it.
But I still believe an INDI driver for sensors installed on a Raspberry Pi without an arduino in between is desirable.