deadcade

https://ntfy.sh/

Easily set up, and easily attached to other things. Simple notifications about whatever is needed, like service health or updates, new posts on public platforms, etc. A simple curl is plenty to send and receive notifications, and it works on Android without requiring FCM (Google infrastructure).

virt-manager only requires access to the libvirtd socket, as long as the flatpak.has that as default configuration (which I imagine would be the case), there's zero difference beteween flatpak and native.