They chose not to after researching options. Pretty sure they decides account portability was a key feature needed and AP doesn’'t do this. As in taking your account and all your posts and data witj you to a new server. I assume there is a technical reason why this would be very difficult to add to AP/Mastodon otherwise they could have just added it themselves.
Not real co-op, but my wife and I have played hundreds of hours of Wildermyth. Its an rpg with generative elements. We love reading out the lines of the characters in terrible accents. The battlr system is turn based so you've plenty of time to discuss what to do next.