How about this, social media platforms must publish their content recommendation algorithms (including criteria for shadow-bans, containment of reach, banning, and so on.) As well as a log of their suspensions and bans and the specific reason for them. Would have bipartisan support. Wouldn't be onerous to satisfy (they wouldn't even necessarily have to host what they publish, it could be hosted on a regulatory agency's site.) And that's just thinking of low-overhead solution off the top of my head. Unfortunately, I think you are attached to the problem too much to accept that there is a solution.