Discussion about the Iris Coq development happens on the mailing list iris-club@lists.mpi-sws.org and in the Iris Chat. This is also the right place to ask questions. The chat requires an account at the MPI-SWS GitLab (use the "Register" tab).
If you want to report a bug, please use the issue tracker, which also requires an MPI-SWS GitLab account. To contribute code, please send your MPI-SWS GitLab username to Ralf Jung to enable personal projects for your account. Then you can fork the Iris git repository, make your changes in your fork, and create a merge request.