But even that will have some status code.
404? 500? 503?
There is a FOSS alternative. ntfy.
I've been running it for a couple of years, if not longer. Works extremely well. The downside, of course, is getting the apps to support it.
The ones I care about already do.
It does.
The IPv6 addresses isn't pingable at all.
Neither the IPv4 or IPv6 addresses respond on port 443.