system settings, then apple intelligence and Siri. Then you see two switch, one for Apple intelligence and one for Siri, you can turn either on or off.
i presume in Goldengate if there is a way to turn of AI, it will also turn off Siri, since they will be linked. I would be surprised if there is not a way to turn it off. I know Apple went though the stage of turning it back on in Tahoe with updates, but that lasted for a a couple of updates.
If it can't be disabled, I will not be updating. not sure if i really need to anyway. Goldengate seems to be more about AI and changing the look than anything else.