My current setup is Uptime Kuma sending notifications via Ntfy.

I need to resolve the issue of what to do when the internet is down (and thus Ntfy cannot be reached), but it has so far done everything I want it to do. It also means I get push notifications on all the devices I care to receive them on.

For what it is worth, yesterday I tried to do place the machine first exactly because of that. The machine complained. I did not insist, since it was faster for my five items to just do what it wanted me to do, but it is possible the setup just does not like it.