We use iOS “Critical Alerts” and similar on Android that breaks through any Do-Not-Disturb settings. https://heiioncall.com/blog/better-alerting-for-heii-on-call... Would you be willing to give that a shot? It wakes me every time :)
(It’s configurable too; we have vibrate-only or silenced modes. Think old-school beeper.)
In the rare case that it doesn’t wake you, we have configurable escalation strategies to alert someone else on your team after a configurable number of minutes.