A volunteer alerted me that https://discourse.wmflabs.org/ is down.
There isn't contact information in the 502 page, so it's not clear who to alert. I'm a fan of bringing this to production (T184461) so we can use it more reliably, but in the meantime it would be useful to get the wmflabs.org version up again, add some informative error pages, and add some monitoring to catch this kind of outage!