this is probably the question of all questions to Jeep Gladiator owners. And I try to answer this as short as I can. Yes, they will fit, even with the stock wheels/rims. After tons of research, I decided to go with 35x12.5R18 BF Goodrich KM2 mud-terrain tyres on my otherwise stock Jeep Gladiator Overland 2020. There is no rubbing at all, not even at full lock.
The tyres fit very well on the stock 18-inch wheels that came with the Gladiator and I think together they look fantastic. Also noteworthy, there is not tyre poke. The wheels fit perfectly under the flares.
There's one thing that I personally like to upgrade, which is getting rid of the factory rake and raise the front by about 1.5 inches. I think this would also mitigate any potential rubbing when having a lot of flex offroad. But I keep you posted. Pictures are attached in the next comment. :)