I would omit the left-wing characterization as a debatable generalization. Perhaps it would be better described as the specific platforms being opposition partisans, rather than the Internet itself.
I'm sympathetic to such an argument, but it does beg the question: Which platforms? The original comments choices of singling out Rumble and Truth Social, would imply that YouTube and Twitter would at least be _among_ those "specific platforms" but neither of those platforms are, at least according to the left, particularly left wing. Both platform have repeatedly been criticized for creating and propagating structures that lead people down what was called "the alt-right pipeline" and has, historically, hosted some of the most active alt-right figureheads.
That's not to say either platform is or was right-wing either. I'm not the one making an argument. Though I'm not convinced they were particularly left-wing or partisan before the creation of Rumble and Truth Social.