I used to work at Dundurn Castle (it's not really a castle).

In the side hall, where we had visitors wait for the next tour, hung a print depicting a 19th century ice harvest.

It showed horse teams on the ice and groups of men using long saws (like a traditional lumberjack saw, but with a handle only on one side), cutting large blocks of ice which were then lifted with massive pincers onto the waiting drays.

The "Castle" had an ice pit. Of course it was no longer in use (the harbour doesn't regularly freeze solid enough anymore even for ice skating much less ice harvest), but we were taught to describe to the visitors how these ice blocks would be lowered into the pit and covered with sawdust. Apparently they would last throughout the summer. I can well believe it as it was always very cool in the hallway outside - even without a deep pit filled with ice.

Edit; I'm very curious about whether First Nations in Canada harvested ice - really hoping someone can answer this question.

I've never heard of ice harvest taking place on the Great Lakes themselves. Ice from ponds would be a much better business proposition. Ponds and small lakes freeze much sooner in the season than the Great Lakes, they are safer to work on, and you can access them from all sides.

I suspect that the ice from ponds would be better quality. Along the shores of the Great Lakes, the waves and wind keep more air to be included. The still water of a smaller lake would trap less air, and give you a clearer product.

This youtube video of ice harvesting at pocono manor in 1919 shows a variety of special tools (horse drawn saw/serrated plow, horse shoe crampons etc.) and methods. Unfortunately it doesn't have sound so no explanation of what they're doing or why, sourced from this metafilter post on the 18th century international ice trade that features further videos on ice harvesting.