I use home assistant and have a dashboard button that triggers an automation.

Using the notification action, I turn off do-not-disturb, turn off Bluetooth (so it doesn’t pipe sound to earbuds or remote audio), set notification mode to on (not vibrate) and set the notification volume to max. I used to loop the default notification sound, but then switched so that the notification uses a new channel entirely and set each phone with a song so it will play for a while. You can silence it with the volume key.

Took a little tinkering to get it right, but works really well.