At least Gibson also posts on Mastodon from time to time, which can’t be said about most of the others. There are some working proxies like bird.makeup but the feeds aren’t updated immediately. The federated Threads accounts are probably the next best.
Why would he be dead? As with the Prigozhin mutiny, he’ll just fly somewhere away from Moscow and hide in a bunker, which could be in central Russia or near China.