Does hand sanitiser work as well as soap, or is that a myth?

It depends entirely on the organism and whether hands are visibly dirty. Alcohol-based sanitiser at 60 percent or more works well against most respiratory viruses and many bacteria, and is genuinely useful when a basin is not available. It performs poorly against norovirus, which causes most stomach bugs, and against Clostridioides difficile spores, and it does very little on hands that are greasy or visibly soiled. So sanitiser is a reasonable supplement, not a replacement — soap and water after the toilet, before cooking, and whenever hands look dirty.