The FTC is a generally complaint-driven agency. I think there's a good case for the FTC to step in and investigate Twitter for unfair and deceptive trade practices for labeling individual instances of Mastodon as malware when people try to link to them on Twitter.

Instance owners don't need a lawyer to do this. Just file a complaint here and say that Twitter is unfairly labeling your site as malware. Then send that to the FTC, spread it here and tell a reporter.

https://reportfraud.ftc.gov/#/