
it does not have any generic access to the file system (it uses portals).
Now why it does not work if Firefox is installed as a flatpak: The very good official Firefox flatpak by Mozilla really does have few permissions for being a browser.
That is, so far, why Firefox installed on the host does work…. Flathub KeePassXC has a patch that allows the keepassxc-proxy to be started via flatpak run, i.e. The only thing it possibly needs to do is get into the KeePassXC flatpak. If Firefox is not sandboxed, that proxy can start as usual. KeePassXC-Browser) and tries to listen on that socket to find messages. keepassxc-proxy is started – via native messaging – by the browser (triggered by the add-on i.e.
KeePassXC creates an UNIX socket in $XDG_RUNTIME_DIR/kpxc_server for applications to listen too. But for the curious, I'll explain the problems we face: If you just want the solution, you can skip this part.