No new services are needed for this. I have been part of many of these over the years. I let them grow organically. I am in many Discord servers and Slack cha

No new services are needed for this. I have been part of many of these over the years. I let them grow organically. I am in many Discord servers and Slack channels, and forums hosted on Discourse. Whenever someone or I want to go through a MOOC in a cohort, or read and code through a book, or work on a project, we just make a post on the forums, and interested people let the poster know that they would like to take part. A new channel is created in Discord, Slack or a new server- sometimes a Telegram channel. And we go from there. More than 70% people drop out in more than 90% cases. But you would find at least 3-7 people for any endeavor. This model is highly successful.