Most technical discussion takes place in #sidechains-dev on Freenode. For other discussions, including ideas and even meetups, the Slack community has several rooms dedicated to these items. There is also the
#irc room, which bridges input directly from the channel on Freenode.
Other resources are listed below.
- https://github.com/ElementsProject/elements - contains isolated feature and dev sidechains braches
- branch alpha - testnet dev sidechain demo