Although an active huidity source in a smoker might be a good ides, I have never seen a smoker with an active humidity control. I don’t think a gauge or sensor for RH control that withstands the smoky conditions and heat inside a smoker exists. Except of just an inside water tray, there are several ways of vaporising a smoker - Meadaw Creek’s Cabinet Sokers for example https://www.meadowcreekbbq.com/catalog/barbecue-smokers/bx25-box-smoker