I am disappointed that Slack was never mentioned in any of this. ID, the “official” OSM editor, recommends that users collaborate on Slack. Is there any chance that OSMF could host a Matrix (or other F/LOSS Slack competitor) alternative?

Yes, I am aware of the current perceived benefits of Slack over Matrix. On the other hand, someone could point out many features the Google Maps has over OSM and suggest that we should just use Google Maps.

And I see a mention of GitLab (the shiny open core Github alternative) but I see no mention of Source Hut, the up-and-coming cloud collaboration suite that may lack Gitlab’s sparkle but it makes up for it in freedom (in my opinion).