Discourse first crossed my path back in 2014 when it was still in beta and I migrated the SitePoint forums from vB to Discourse. It’s still going strong.
https://www.sitepoint.com/community/
Next on my list was the UX Mastery community, which I also migrated off vB and is still going strong.
https://community.uxmastery.com/
Anyway, it’s pretty obvious how this story ends. 