I think it should be applied to media and social media. You could run a radio ad in a small market and not identify yourself as a third party or be registered, and Elections Canada might not find out about it. You could do that in a community newspaper possibly and Elections Canada might not see it. They would probably see TV ads.
Just require all media companies and all social media companies to report every election-related ad to Elections Canada for six months leading up to an election. Give them the power to stop false ads, and stop an ad that doesn't identify the third party. They have to know who paid for it. They have to know where it was targeted as well, all the details. Then they'll be able to also enforce the spending limits that would apply in the pre-writ period.
Otherwise they won't know about the ads. The rules will be there. Just don't leave it to the social media companies especially to self-regulate, because their incentive is to make money, not to stop an ad because someone may not like it.