The way these rules get enforced against large corps is through restricting their ability to make money from Canadian sources, because they can limit the Canadian bank accounts and/or business licenses that are required to collect money here from advertisers.

For a Lemmy instance that has no financial ties to Canada, there's no enforcement mechanism. Even the Canadian based instances may not be operating as businesses, and if they have no income, it's almost impossible to enforce anything. A few donations collected through an individual often can't be targeted.