DemocracyOS - online decision making
This might be close-able since the DemocracyOS project hasn't seen much in the way of serious activity for quite some time, especially around security updates, which is usually a good barometer of earnest maintenance.
Yea, it's been a couple months since last update (Dec 2018.)
Probably can remove this one from the list - it's been carrying a "no maintenance" notice on it and has been abandoned code-wise since 19 December 2018, and that death-notice banner went into the readme 05 May 2020.
Or as a GIF:
On the plus side, decidim is still alive and well.