The article says, for the most recent week that data is available:
"In total, for the week from June 15 to June 21, there were 170,998 people coming into Canada at a land border crossing, and most of those were commercial truck drivers. The comparable period last year saw 1,217,845 people crossing. Of those land crossings, 104,247 were truck drivers."
So about 10,000 non-truck drivers a day along the entire US-Canada border. I would expect most of these are Americans doing essential work in Canada. I understand that at least a few thousand Canadians cross the border at Windsor alone each day to do essential work in the USA. Works both ways.