This is a good test:
Take your wheel off, inflate to between 20 and 30 psi based on your best judgement. Grasp the tire with both hands, with the web of your thumb and forefinger of each hand overlaying the tread. With your full body weight, press down as hard as you can and try to feel the rim (without squeezing with your fingers). Given all your weight and strength, you should be able to just feel the rim. If its too easy, add a few lb/in² and try again. Too hard, let a small amount of air out.
This should be the correct pressure for optimal traction with tubeless tires, without bottoming out on roots and rocks, given proper technique. If you are riding trails that are appropriate for your skill level this should be a good starting point, and only add pressure if you find yourself bottoming out.
I find that for my weight of 160 lb, this is around 20 psi. Because I ride a hardtail or rocky terrain, I cheat a bit and put 18 in the front and 22 in the back, for a little extra grip up front and a little more rim protection out back.