I suppose it won't apply to 4chan, Hacker News, Bluesky, or mastodon.social — because it can't. They're big enough that it's hard to imagine what excuses will be made for ignoring services like these, which do meet the official definition of "social media" but are influential enough that they can't really just ban Canadians from using them. There is no way they're all going to be lining up to submit a Digital Safety Plan to Canada's new Internet Protective Services department.
This thing is written for (and probably by, considering the selection of experts the consultation process heard from) the multinational social-media giants that dominate the landscape today. If there is ever to be a better future for the Internet, this bill simply ensures that it won't be developed in Canada.