I'm on the development team for OpenColorIO, and would like to raise the conversation around project communication platforms. Quickly looking at the Collaboration Tools list for ASWF I see the usual options of Mailing Lists and Issue Tracking. However, OCIO has greatly benefited by having real-time communication through a Slack group which promotes candid responses from maintainers and community members instead of long essays like this. I believe this fosters a greater feeling of participation and community which was very helpful in re-kindling development with the project.
I'm am definitely not a proponent of Slack. In fact, I really dislike it and am starting the conversation with our community on switching to an alternative. When/if OpenColorIO is moved under the care of the ASWF, I would like to see a real-time communication platform promoted. At the moment the best option which I have yet to use in practice is Zulip (https://zulipchat.com/for/open-source/).
The features they offer seem to be a substantial gain over Slack or alternatives.