There was a comprehensive literature review posted on /r/coronavirus some two months ago that strong (and statistically robust in my opinion as a professional data scientist) indicating that smokers were less likely to be infected with the virus, with possible mechanisms from previous viruses like SARS and MERS.

In fact that was one of the earliest common sources to mention ACE2 receptors. A month or so later there is at least one study looking at nicotine patches as prophylactic and/or treatment for covid. I'm having trouble finding the reddit thread, standby.