Bensmom, I don't have an instant pot, but cook a whole chicken at least once a month, usually in the crockpot.
The rub I use, which I also use for turkey/bone in turkey breasts:
2 tsp salt
2 tsp paprika
1 tsp onion powder
1 tsp garlic powder
1 tsp ground thyme
1 tsp white pepper
1/2 tsp cayenne pepper
1/2 tsp black pepper (or so, I just guess with fresh from the grinder)
I usually do a really big chicken so that I can use leftovers (7.5-8 pounds) so for a smaller chicken I would use less. I rub inside and out, and a loosen the breast skin and put a little under that. I put a whole or half onion in the cavity, depending on what will fit. You can reduce the salt to a teaspoon if you want - there is some difference, but I am a pretty good taster. It isn't too spicy for my kids, but I have reduced the cayenne a bit for other people.
I use this so much that I just buy bulk spices at the Amish grocery now and keep a big batch.