My compatriot Wayne Witzel pointed out to me how his team at Octant publishes their meeting notes and I think it's fantastic. They publish their notes right into GitHub. Here's a specific example, one thread per meeting.
I really like this for a few reasons:
Single source of truth, no need to link gdocs or hackmd.
Clearly you'll want to use hackmd for the notetaking so you can do it as a team and let people contribute and dive in, this seems like a great way to archive notes. Compare this to how Kubernetes archives our community meeting notes.
If someone from the community has a question they can ask right in GitHub
This is nice, having your notes right there and people can just reply with questions, thumbs up, or do whatever. It's unified, I don't have to subscribe to a list, or know anyone's email addresses. "We announced a thing and people responded with heart emojis" is a much better thermometer for what people are into than sending something to a list.
It costs me almost nothing to give Wayne a heart on GitHub, but I would never send a "This looks great!" response to a list because I don't want to waste people's time.
Little things
Notifications! A searchable archive! Also when you do "We fixed issue #1234" it will know what to do and autolink, which you have to do by hand if you're using something else.
Downsides to consider
This is beta still, and while I do love the idea of discussions being baked into GitHub, you don't get the thorough features and tools that you would by using say Discourse.
Also you probably already have a mailing list. On the one hand, having open mailing lists is a traditional open source thing to do. But I couldn't help but raise an eyebrow thinking about how we can effectively do the same things without the email baggage.