Topics related to the software stack (Key4hep), datamodel (EDM4hep/PODIO), event processing framework (Gaudi), …
If you have encountered a bug and have also already identified where that bug lives (i.e. in which github repository) feel free to open an issue in the corresponding repository directly. In case you are not sure what the correct github repository is open one in https://github.com/key4hep/key4hep-spack.
Most technical discussions happen at the Key4hep meetings and some asynchronous discussions also happen on the Key4hep github.