How (un)safe is it to ride barefoot?
It may well become uncomfortable after pedalling for some time, so don't rely on a quick test ride to check.

More importantly though, you need to be able to stop the bike based on the need to stop, and put your foot down without examining the ground for broken glass, thorns etc. It's not completely unknown to strike the sole of your shoe on the ground, like pedal strike, and this would hurt quite badly in bare feet (there's one roundabout I've done this several times, due to a combination of the camber, turning onto a hill, and having to pull away fast because of a poor line of sight). If you ever bump your foot on your front wheel turning at low speed, that could become unpleasant too.

Let's face it, all cyclists get stinky shoes and feet . And a bad smell doesn't mean a fungal infection. Letting your feet and preferably shoes dry out at the end of each day is a big help. That's the time to go barefoot