This is DeltaChat desktop client but not with the default Electron. Compile instructions for Debian, Arch Linux and openSUSE. One Linux distribution has this packaged : NixOS, package name kdeltachat-unstable. The software developer is also active in the DeltaChat forum. Posting this here to give this project some more attention cause it would be nice to see less Electron and more Kirigami (or Tauri ?).