There are only 3 copies of Electra 11.3.1. no, there will not be public beta testing, and no, there will be no developer build. Only the final release. Developers wanting to update their tweaks for Electra early are recommended to get an iOS 11.1.2 device until then.
Electra Team member nullpixel also teased some screenshots of a working Cydia application on Twitter today.
This feels really good! @coolstarorg good work on the bug, @Pwn20wnd great cli to exploit it :)
Nullpixel confirmed that the team was waiting on a rootFS remount from Jonathan Levin. We'll post more details as they become available. Please follow iClarified on Twitter, Facebook, Google+, or RSS for updates.