This is an interesting hypothesis. Anecdotally, I noticed that here in San Diego, many fewer homeless people contracted COVID-19 than might have been expected, and all that I can imagine they had in their favor was sufficient sun exposure.
My unproven , untested lame theory is that they smoke more , more sun and have also have a lower BMI .
Just tossing in the nicotine theory that is floating out there in case folks had not seen it ... I realize smoking may actually cause it more than help so a bit of tongue in cheek
https://www.cebm.net/covid-19/nicotine-replacement-therapy/
“Nicotine may bind with the ACE2 receptor, particularly in people with COVID-19, and thus could interfere with further SARS-CoV-2-ACE2 binding (pre-print in silico study)
Nicotine and cigarette smoke decrease levels of ACE2 in multiple organs
Cytokine storms could be prevented or suppressed by nicotine through its impact on the cholinergic anti-inflammatory system; nicotine may inhibit hyperinflammation and platelet reactivity“