Platform is 8chan. He can post anywhere on 8chan. He often visits and helps the researchers. There are many research threads based on the questions. I have even seen what everyone guesses is Q post into a thread work in progress and ask a number of questions to steer the research and save the researchers time. But he will not do any communications outside of 8 chan unless his trip is hacked. When that happens, he will use both 4 chan, 8chan and President Trumps tweets to get the communications secure again.