I think this is unclear, as the CRTC isn't expected to have the actual policies developed until sometime next year.

However, this is in the text of the bill:

6 This Act applies in respect of a digital news intermediary if, having regard to the following factors, there is a significant bargaining power imbalance between its operator and news businesses:

(a) the size of the intermediary or the operator;

(b) whether the market for the intermediary gives the operator a strategic advantage over news businesses; and

(c) whether the intermediary occupies a prominent market position.

I can't imagine this ever applying to decentralized social media.