Greetings,
Do Not Disturb on my phone is set up so that starred contacts can reach me, either by calling or messaging.
When I get a Signal message, I get notified with sound, but when I get a regular SMS there's no notification. Only when I open the standard GOS messaging app do I realize I missed a message.
Battery saver is off and sound volumes are normal – nothing's muted.
On a Pixel 7a