You should be able to disable these alerts via the Wireless Emergency Alerts.
She ended up disabling the alerts entirely, which seemed a shame to me, but the ear splitting siren every 5minutes wasn't really conducive to our sanity or our dog's or our ability to actually hear the weather radio.
Moreover, it's a huge pain to get to the history of emergency alerts, which seems like a design flaw. Surprising how poorly a critical life system can be designed.
Yes, GrapheneOS of course allows this.
Edit: re followup comment.
No, adb cannot be used in all cases to disable the packages involved. At all. Some phones refuse to lets users disable some packages, no matter what.
Yes, I know what I'm talking about.
As someone with decades of Linux and Android experience, who often works nights, having Quebec police use presidental alerts... CRTC regardless, to warn of a child abducted by a parent 2000km away from me, is an exceptionally strong motivator.
The sheer stupid of an alert you cannot control the volume, sound, and length of in any way, is absurd. Try going back to sleep after something screams at you, at your equiv of 2am is madness.
By god I hate those alerts.
So yes, I know. If you don't have root, and the phone won't let you disable some packages, you're done.
And it's another reason I like GrapheneOS.