Kudos for trying to address the issue, late is better than never. If you believe there are possible risks if the methods were used, the first things to do would be a retraction, since an erratum/corrigendum presuppose the consistency of the conclusion. Acting quickly could also prevent legal troubles.
The authors say "non negligible" though. And it's a simulation study.
Besides in the limitations section they acknowledge the absence of literature on many biological parameters.
My prior for fomite transmission in respiratory viruses is very low: 1988 article on Rhinovirus, hamsters SARS-CoV-2 study, human case series
I don't have time to make a serious review though.
As an aside, though it addresses the actual question, I'm developping a model to do precisely what you ask: providing health guidance and dashboards tailored to the desire to know yourself, propensity to risk (or better risk aversion) and data you can generate. I'm focusing on the PoC and business side for now, so can't discuss the specifics here.
As you said, it's a cohort study. The cohorts are pretty different (gluco/condro users were more white, educated, non-smorkers, physically active than non-users, though pretty older in comparisons) and the adjustment could be skewed by the small number of users.
But, it's mostly harmless and the effect size looks promising.
Personally I'd make a quick review of the literature to decide whether to commit to taking the supplement and set up an alert on Pubmed.
New paper on downstream viral load stratified by source and severity
The evidence on viral load is still poor https://www.cebm.net/covid-19/sars-cov-2-viral-load-and-the-severity-of-covid-19/
Remdesevir (lopinavir + ritonavir) (HIV)
A little mistake with the parenthesis, they're different things
Interesting question. I found this article https://arxiv.org/abs/1802.07740 together with the papers that cite it https://ui.adsabs.harvard.edu/abs/2018arXiv180207740R/citations as a good starting point.