I have a 2022 Silverado LTD with the 3.0L Duramax and mine has a moldy smell also after it rains. I've brought it to the dealership and they could not find a leak. The only area I have not confirmed is clear is the A/C drains. This is a frustrating mystery I would like to solve. I love the truck otherwise.
Did you have any luck getting rid of the smell?