Ask HN: What is best alternative for Google Groups?

Please check out: https://groups.io. We support markdown/code syntax highlighting, Github integration, member sync with Slack, and lots more.

NodeBB[0] and Discourse[1] are good alternatives... They have a lot of integrations including github and syntax highlighting

I recently moved a google group to Google Plus Communities[0]. It's a free option and all your community members already have a google login.

This wouldn't work for larger projects, but if it's a smaller project, maybe Slack[0]? It has a pretty good free-tier as well.

Discourse maybe a good choice: http://www.discourse.org/

You will need to pay to host it though.