Lightroom Classic keeps importing my photos with a preset that I did not apply

What preset do you feel is being applied? What is happening to your images that makes you feel this is happening? Are these raw images?

It sounds as if you have at some point saved certain settings, as your default LR processing for that camera, with Set Default (as below).

The way to find out, is with a new import, hit Reset in Develop. This button re-applies whatever are the current defaults, for that type of image (different for JPG than for Raw, different per model of camera, also can be different per camera serial number / per ISO setting if LR is so configured). If a develop preset was applied during import or later, or if Auto Sync is on and you've applied changes unknowingly other than processing defaults, those changes will get cleared by a Reset.

If you still see the unwanted adjustments after Reset then you can change things individually to what you do want; or else you can return them wholesale to the originally installed default processing by holding Shift key - temporarily changing "Reset" button to "Reset (Adobe)".

Once you've got the processing looking how you want pictures of this kind to initially look in the future - as the Adobe default or else different from that, whatever you like - hold the Alt key (Option on Mac) and Reset button changes to "Set Default". Clicking this updates the processing default. New imports will look like this, or existing imports can be set to this same starting point by simply clicking Reset.