This special release of Conversations remains on the 1.23.x branch and will provide the same user experience as it was prior to Conversations 2.0.0
The source code can be found here: https://github.com/siacs/Conversations/tree/legacy
If you are new to Conversations you should check out the regular releases called »Conversations«
Conversations Legacy is only suited for a small audience that can not live without the features that have been removed in Conversations 2.0.0 most notably:
» Customizable Resources
» Swipe gesture to open the conversations overview.
Everyone else is strongly recommended to use Conversations instead.