I had read about potentially protective effects of nicotine [1], but seems like it was a fluke
https://www.nature.com/articles/s41533-021-00223-1
[1] There is even a RCT on this, but no results yet https://clinicaltrials.gov/ct2/show/NCT04583410
At the same time early in the pandemic I remember reading that being a smoker had a moderate impact in reducing COVID symptoms severity.