I live in Gent, Belgium, which has more bike traffic than car traffic on any given day. Biking here is treated as a way of life. I've been spoken to for biking without a mask, even though I was not in a heavily populated area (I was riding along a canal outside of the city, and was accosted by a police officer riding in the opposite direction).

But even so, so what? The mask isn't going to let me ride as vigorously as I normally would, but I can still get out into nature and enjoy some exercise and new scenery.