Truck camper off truck on slope

You have to check to see if it slides. I'd at least put something like rubber or stall mats under the jacks to prevent them from sliding. My driveway has about half that slope, but I've never tried taking it off. My street is almost flat, so I do that instead.

You could try jacking it up to see if it stays put or not.

not worth the chance of dropping it.

What size camper?
Having big campers - I had to straight up the front jack more than once. It was dualy extensions that bend.
That said 2-ton weight is not something you want to fool with, so in your case I would build some high-friction pads that would make horizontal surface for your jacks.