“Duck Duck Go” has some answers:
https://pubmed.ncbi.nlm.nih.gov/23948436/
https://www.news-medical.net/health/COVID-19-and-Smell-Loss-(Anosmia).aspx
https://www.bbc.com/news/health-53810610
https://www.healthline.com/health/anosmia#causes
Interesting, reading the second one now. I meet quite a lot of people that have had Covid and loss of smell seems to be pretty common among them though not universal.