I've had really good success with discord + Trello.
We made a couple meta categories where we put all the pallette, setting, etc info, a begin and end column, then added periods events and scenes as normal, labeling as we go. We added a label for light/dark as well.
Not super elegant, but simple and low-friction.
For example:
I recommend using Trello for managing "the board". It is a great collaborative tool.
Here is an example of the Microscope game that we did to kick off a campaign: https://trello.com/b/Ic8j0wvm/royal-pride-of-musketeers-microscope
For communicating, that will vary by group. Personally, I like video, so we use zoom.us to talk.
>If there are other ways than Roll20 obvious to y'all...
Well, someone made a schema on gingkoapp. I've never had the chance to try it so I'm not sure how good it is.
We've used https://gingkoapp.com/ in the past and that worked well. Trello is a similar option that might work okay. Takes a bit of adapting compared to the way it's described in the rules but it worked well for us.
I use gingkoapp when outlining for myself or playing microscope with friends. I don't have the time right now to commit to a game, but would be open to it in the future.
Example Microscope game: