Interesting, just saw on #chaosevents:matrix.org that yesterday moxie gave a talk about why Signal is not federated (https://cdn.media.ccc.de/events/eh2019/h264-sd/eh19-197-deu-ActivityPub_the_Fediverse_and_Everything_sd.mp4) but it is not available :(

https://media.ccc.de/v/36c3-11086-the_ecosystem_is_moving
https://www.youtube.com/watch?v=DdM-XTRyC9c

Does anybody know why?